C – Abbreviation for “clean to the unaided eye”. See CLARITY GRADE.
cable – String or cord of twisted rope, metal or gut connecting power source to the train of wheels in a timepiece.
cable fluting – Round moulding worked in the flutes of a column.
cable girdling – Rope-type decoration circling a silver piece.
cabochon – An unfaceted form of cutting, used for opaque and translucent stones; the stone is given a rounded, convex shape, and cut high or low for best effect. Stones that contain needle-like, parallel inclusions as a single set or on three 60°- intersecting sets are cut in a high cabochon to bring out the eye or star; moon-stones and opals are best cut low. Poor-quality specimens of many stones that are usually faceted are often cut in this shape.
cabra stone – (kabb’-ra) Fluorite.
cacholong – (kash’o-long) Or cachalog, an opaque bluish-white or porcelain-white variety of common opal. Unimportant as a gem.
cadmium – An elemental metal used as an alloy in gold solders to promote easy flowing under heat.
cadrature – Striking word under the dial but often used to refer to striking work on outside back of clock movement.
cairngorm – (kairn’gorm) Smoky quartz. A stone of a smoky gray or brownish color, not to be confused with the yellow citrine. It is a popular Scottish stone and was named for the locality, a mountain, in the streams of which waterworm crystals are found.
calamine – (kal’a-meen) A name about which much confusion has arisen. In the United States of America calamine is synonymous with hemimorphite and is a silicate of zinc, an ore of zinc but not a gem mineral. In Europe, calamine is the name applied to the carbonate of zinc, here called smithsonite, and sometimes used as a gem despite its softness.
calbenite – See MYRICKITE.
calcite – (kal’site) A common mineral, calcium carbonate, and the principal constituent of limestone and marble. It has a strong birefringence, and clear crystals, known as Iceland spar, are used in the polarizing microscope and the dichroscope. Some varieties, often colored by natural or artificial impurities, are used as a decorative material. Onyx marble is a banded variety. Mexico onyx, Mexican jade, Atlas pearls, calcite prism pearls and cerulene are other name often applied to calcite.
calomalachite – (kal’ko-mal”a-kite) Mixture or malachite, calcite and gypsum, sometimes said to be used as a decorative stone.
calendar mechanism – Wheels, leaver, and plates to indicate day and dates in a time piece.
calendar, perpetual – Timepiece calendars which provide for unequal months as well as the 29th of February during leap years. See BISSEXTILE.
calendar watch – A watch that shows the date, day of week or longer intervals. More complicated mechanisms show month; adjust for month lengths and lead years; show phases of moon, positions of stars, times of sunrise and sunset each day, difference between solar and mean time, and tidal changes.
calf’s head cut – A fancy diamond shape, a tapering baguette with the wide corners truncated.
calibrate – To adjust a measuring instrument by comparison with an accurate standard.
calibrated – Stones, usually colored, cut to precise dimensions for mounting in machine-made setting.
calibre – (kal’i-bray) 1. Small colored stones in rectangular or square shapes used adjunctively in the decoration of a piece of jewelry, rather than as the central motif, or set in band in guard ring. Also sometimes used in the trade to designate small colored stones of “fancy” shapes. 2. Size and factory number of a given watch movement.
California iris – Fanciful term for kunzite variety of spodumene.
California jade – Misnomer for californite.
California lapis – Usually a misnomers for a mixture of blue dumortierite and quartz. True lapis luzuli has been reported from California.
California moonstone – Chalcedony pebbles.
California onyx – Dark brown banded calcium carbonate, aragonite.
californite – A compact variety of green vesuvianite which can be cut and polished much like jade, which it strongly resembles.
caliper – 1. Usually a measuring tool with adjustable jaws that embrace the object being measured. 2. Horology. a. A tool for holding watch balances while truing them. b. English term demoting the design or type of a watch or clock movement, or of the gear train of a timepiece. See BOLEY GAUGE, GROSSMAN GAUGE, VERNIER, JEWELING CALIPER ATTACHMENT, DIAL GAUGE.
callainite – (kal’lane-ite) A mineral, related to turquoise found in a Celtic grave in Brittany. The source of the mineral is unknown. It is translucent, apple to emerald green in color and some has been cut as a gem stone because of its historic interest. It is of no commercial significance, because of its rarity. The name is from the term callais, used by Pliny.
cam – An irregularly shaped plate in a mechanism, which rotates to give variable motion to another part pressing against the cam. Example: The heart shaped piece that returns sweep-seconds hand to zero in a timing watch.
Cambay stone – Carnelian from Cambay, India.
camel’s hair pencil – A small round brush for applying flux or other materials in jewelry work.
cameo – A stone, usually composed of two differently colored layers, which has been carved so that a raised image in one color stands out in a background of another color. Cameos are principally cut from a variety of agate with flat bands, dyed and known as onyx or sard-onyx. These are known as stone cameos. Shell cameos are cut from shell with similar colored layers. Shell is softer and more easily cut than agate. Cameos are molded of Wedgwood porcelain, of lava, and of glass. The glass cameos are often made in imiatation of the cut stones cameos. “Molded” or “pressed” cameos should be so described. “Assembled cameos” are made of two natural stones cemented together. “Assembled imitation cameos” are the same with one or more parts made of glass or plastic. See INTAGLIO and CHEVEE.
cameo shell – Shell of any of several large conchs, commonly the bases of shell cameos.
canary diamond – A fancy diamond with a strong, pleasing yellow color. The Tiffany diamond, a square-cut brilliant of 128.5 carats, is the largest known canary diamond.
canary beryl – A greenish-yellow beryl, but the name has no standing and its use is undesirable.
canary stone – A yellow carnelian.
cancrinite – (kan’krin-ite) A complex silicate mineral sometimes used as a decorative stone or cut cabochon for collectors. Litchfield, Maine, cancrinite is yellow and is associated with white feldspar and blue sodalite; elsewhere it is white, pale violet, pink, or deep blue.
cand – Blue-john fluorspar, also called cann and kann.
cannon pinion – A hollow cylinder with pinion leaves as its lower end, most often fitted friction-tight to the center post extension of the center pinion of a watch or clock, and forming the first member of the dial train, with its leaves engaging the teeth of the minute wheel. The minute hand is usually fitted to the top shoulder of the cannon pinion. Sometimes spelled canon, as in French.
cant file – A file with edges that are smooth or “safe”.
canutillos – (kan-oo-teel’yos) Colombian term for fine gem emeralds.
cap – 1. Inside cap, an extra cover hinged to a watch case center, inside the outer cap or “back” of the case. 2. Dust cap, a metal cap bolted over the movement of some English watches to cover the movement and protect it from dust. 3. The sawn-off top of an octahedral diamond crystal.
cap, dust – The cover over a watch movement to exclude dust, lint, moisture.
cap jewel – Also called end stone. A flat un-pierced stone placed over a hole jewel to make contact with the end of a pivot. The cap jewels over both pivots of an arbor limit its end shake and minimize end friction compared with the greater friction of shoulder pivots without cap jewels.
capacitance – The capacity to receive an electrical charge as in an electrical timepiece.
capacitor – A device for accumulating an electrical charge; usually two conductors separated by a dielectric. A condenser.
Cape – A color grade of diamonds, the third to fifth major grades (Light Cape or Silver Cape, Cape, and Dark Cape) with yellow tints are known as Cape diamonds. They are preceded, in some scales, by First or top White, and followed by First and Second Bye. See CLARITY GRADES.
Cape ballas – Ballas from the African mines.
Cape chrysolite – Prehnite.
Cape emerald – Prehnite.
Cape garnet – Pyrope garnet from South Africa.
Cape May Diamond – A misnomer for a rock crystal from southern New Jersey.
Cape ruby – A misleading name given to the ruby-red pyrope garnets found in association with the diamonds in the blue ground.
capillarity – An effect of molecular adhesion and liquid surface tension whereby a liquid tends to press into the narrower part of a space, as between two walls standing at an angle to each other. Pivot bearing and jewels are formed to take advantage of capillarity feeding oil to point where friction requires lubrication.
cappe – (kap-pay’) Octachedral-shaped cleavage. Dutch term.
caput mortuum – Iron oxide, for polishing.
caracoly – (kar-a-koll’-y) An alloy of gold, silver and copper, used by the Carib Indians.
carat – A unit of weight for gemstones. Although it has varied in the past, the now generally accepted standard is the metric carat, one-fifth of a gram (200 milligrams), which was adopted in the U.S. on July 1, 1914. The metric system divides the cart into 100 parts, resulting in such decimal weights as 0.24 ct., 1.35 cts., and the like. Prior to acceptance of the meteric carat, gem ddealers had divided the carat into 64 parts and wrestled with such time consuming fractions such as 13/64 ct. or 1 44/64 cts. The word carat comes from the seed of the carob tree, the Biblical locust (Ceratonia siliqua), which was used by ancient pearl- and gem-dealers as a unit of weight. There are 142 carats to an ounce avoirdupois. This word is not to be confused with karat, which denotes the ratio of fine gold in an alloy. See CAROB; KARAT.
carat goods – Diamonds parcels in which the stones average one carat each.
carbon – 1. An element. Diamonds, graphite and carbon black are all carbon; the carbonates, like calcite, contain some carbon in combination with other elements. 2. In the trade, carbon is used as an abbreviation of carbonado, and apparently black inclusions in diamond are called carbon spots, although, as Eric Bruton, observes, very few if any are carbon and only a few are truly black. The black look often comes from the reflection of light by cleavages or by colorless, transparent included diamond crystals, the true nature of which is seen when the stone is examined under magnification in dark-field lighting. Many carbon spots can be made less conspicuous by laser drilling and solution.
carbon pin points – Trade name for small apparently black specks in diamonds.
carbon steel – Steel with a comparative high carbon content used for springs and cutting tools.
carbonado – (kar-bon-ah’doe) Black porous diamond, resembling coke in appearance. It is a mass of small crystals, often harder than ordinary diamond and very valuable for cutting purpose. It ranges from dark gray to black in color. Much of it comes from Cincora district of Brazil. Also called carbon and carbonate in the trade.
carbonate – See CARNON. Also a trade misnomer for carbonado.
Carborundum – A brand-name of an artificial abrasive material, between 9 and 10 in hardness, made by fusing and crystallizing sand, coke, and sawdust in an electric furnace, producing silicon carbide crystals that are pulverized into abrasive grains of assorted sizes, used in granular form, and made into grinding wheels and stones.
carbuncle – A name of the Middle Ages which referred to any cabochon-cut red stone. Rubies, spinals and garnets were included. Today it is generally used with reference to a cabochon-cut garnet. See KARFUNKEL.
card jewelry – Jewelry prepared for sale by pinning or sewing the goods on cardboard, as an aid in displaying the goods; characteristic of medium and low-priced rather than of fine jewelry.
carmen bracelet – Bracelet composed of pivoted links each enclosing a spring, normally closing the links together to close the bracelet, with a pantograph action, to accommodate the bracelet to a variety of wrist-diameters. This type of bracelet was popular as jewelry about 1905, when the earliest bracelet watches in the U.S.A. appeared in the comibination of a camen bracelet with a watch movement in place of the usual locket or medallion on the bracelet.
Carnegie Gem – Trade name for a diamond imitation consisting of a doublet with a crown of synthetic spinel or sapphire and a pavilion of strontium titanate.
carnelian – Sometimes spelled cornelian. 1. A reddish brown, orange brown, or yellow brown variety of chalcedony. Used in inexpensive jewelry and in carved Chinese objects. Its grades into sard with increasing brown tones. The color is caused by iron oxide. Lighter red to yellowish red and less translucent carnelian is called female carnelian while the deep red, more uniformly colored material is sometimes known as male carnelian, oriental carnelian, or “carnelian from old stones.” The correct name, according to G. F. Herbert Smith, is the word cornelian, having been derived from the Latin word cornum (cornel berry) rather than carnem (flesh). 2. To the trade, a synonym for sardonyx.
carnelian onyx – Agate with red and white bands, sardonyx.
carriage clock – A small clock with balance instead of pendulum, usually with a leather-covered carrying case for portable use, formerly carried on journeys by coach or carriage.
carrier – A clamp to rotate work held between centers in a lathe. See DOG.
cartouche – (kar-toosh’) 1. A symmetrical ornamental tablet used in decoration or in engraving. 2. In horology, a porcelain plaque for a clock or watch dial numeral. 3. A conventional figure, usually symmetrical, enclosing a maker’s mark.
carving – The forming of a design in metal or other material by cutting away the background. The design if formed by the material left after the background is removed.
carving wax – Extremely hard wax used for carving, drilling, sawing and filling in making wax models. See MODELS.
cascalhos – (kas-kal’yos) Portuguese name for gem-bearing alluvial sand and gravel deposits.
case – The protective box covering the mechanism of a watch or clock.
case-screw – A screw, with full or three-quarters head, to fasten watch movement in case.
case spring – 1. In a hunting watch case, the lift spring that opens the lid when the crown is pressed. 2. The lock-spring with a latch, released by pressing the crown, to allow the lift spring to open the lid of the hunting watch case.
case stake – A steel anvil held in a bench vise, for forming or repair operations on pocket watch cases. Case stakes are made of varying shapes to enter all part, forms, and sizes of watch cases in manufacturing and repairing operations.
cassiterite – (kas-sit’er-ite) The ore of tin. Crystals vary from black to light brown, yellow, or grayish brown in color; rarely, clear crystals have been facet-cut for collectors.
casting – 1. A process for forming an object by pouring melted metal into a hollow mold; often used for duplicating a piece of jewelry, using the original piece as a pattern for making the mold. 2. The process of manufacture in which molten metal or ceramic slip in poured into a mold for the purpose of shaping. 3. A process for forming or duplicating jewelry objects by forcing molten metal into an investment mold from which the wax pattern has been burned out. Pressure may be applied by centrifugal force, air, strem, or a vacuum beneath the mold. See LOST WAX; TREE.
casting wax – Wax, specially formulated for use as patterns for casting. See LOST WAX.
castle-wheel – In chronograph watch mechanism, a steel wheel with several notches on its edge, superimposed on a toothed ratchet, the whole piece moved by a click operated through a lever by the crown or a button outside the watch case, and with a pawl that is operated by the notches to engage or disengage gearing, ect., in the chronograph mechanism.
Catalin (kat’a-lin) – A plastic with the same uses as bakelite, etc.
Caralina sardonyx – See CATALINITE.
catalinite – Variegated jasper pebbles from Santa Catalina Island, Calif.
catch – 1. A hook on a brooch, bar pin, or other piece of jewelry, that engages an end of the pin that holds the piece to the clothing. 2. Safety catch. A catch that has a hinged or sliding piece added, to look the pin in the catch to prevent loss of the piece of jewelry through accidental unhooking of the pin.
catgut – Twisted animal fibers used as cables or power connectors in clocks.
cathode – A terminal by which an electric current leaves the substance through which the current passes; the negative pole. In an electroplating bath, the object being plated is the cathode. See ANODE.
cateye – The low cabochon-shaped bit of shell used by the Turbo snail to close its opening. See OPERCULUM.
cathedral gong – Spiral wire gongs or rods in a chiming clock.
cat’s eye – The name given to a gem which, when cut cabochon, shows a single light streak across its face. It is caused by innumerable parallel inclusion, of minute needle-like crystals or of tubular cavities, the sides of which reflect light. Cat’s-eyes are known in many stones, but the unmodified word refers to chrysoberyl. Tourmaline cat’s-eyes, beryl, diopside, and scapolite cat’s-eye are not uncommon. See TIGER EYE, BAVARIAN QUARTZ, HAWK’S EYE, ORIENTAL CAT’S-EYE, CYMOPHANE, ASTERISM, CHATOYANCY, OPERCULUM.
cat’s-eye opal – A flash-fire opal cut as a high cabochon which results in a cat’s-eye effect.
cave pearl – Rounded bit of onyx marble formed in a pool on the floor of a cave. Rarely of any gem significance.
cavitation – In ultrasonic cleaning, the creation and collapsing of tiny bubbles (cavities) to cause a scrubbing action.
cavity – Diamond grading. An equidimesional opening in the surface of a polished diamond, sometimes caused by a blow or the pulling out of a knot in polishing.
c-clamp – A sturdy open ring used as a restrainer for the wound mainspring to ease assembly or dismantling.
celestial stone – Turquoise.
cell – A single electrical energy unit (cell). See BATTERY.
celluloid – A plastic compound of camphor and guncotton, highly inflammable and dissolved with acetone.
cement-brass – A brass piece to be held in a lathe chunk, on which is cemented work of irregular shapes which cannot be held in a split chuck. Cement basses are made of various sizes for holding flat and cylindrical.
canter – In a watch case, the circular part holding the movement and on which the back and front caps or bezels are hinged, snapped-on or screwed.
center arbor – See CENTER PINION.
center, dead – In a lathe, the center points of which are motionless.
center distance – Distance measured between the exact centers of motion of a pair of gear wheels, or a wheel and pinion that work together. This measurement is equal to the sum of the pitch-circle radii of both members of the gearing, and each radius is proportional to the number of teeth or leaves in its wheel or pinion. The heights pf addenda are of course not included in measurement of the canter-distance. See ADDENDUM.
center drill – A drill with an extension bit to drill center-guides in objects held in the lathe, sometimes in preparation for live or dead center turning.
center, live – In a lathe, the center point of which turn in bearing and carry the object upon which work is to be done.
center pinion – The pinion in the train of a watch or clock of usual design that is driven by the main wheel of the power plant, which a prolongation that carries the minute hand and the cannon pinion of the dial train.
center-post – Center-arbor; or the center pin. A prolongation of center pinion through the dial train and dial, carrying cannon pinion and minute-hand. In earlier European-made watches the center-post in sometimes a pin fitted friction-tight in a hole through the entire length of the center-pinion, with a squared lower end for key, to set the hands.
center punch – A steel punch with a v-shaped point, for marking locations on metal work and for starting holes to be drilled.
center-seconds – A hand indicating seconds read on the minute dial, its motion concentric with that of the hour and minute hands. See SWEEP SECONDS.
center wheel – A toothed wheel fastened to a center pinion; it drives the third pinion of the train.
centers – 1. Lathe centers-steel tapers with V-points, held in female tapers in lathe chucks, tailstock spindles, etc. 2. Locations of centers of motion for rotating parts in watch and clock mechanisms.
canters, line of – 1. In gearing, a line representing the center-distance. See CENTER-DISTANCE. 2. In representing an escapement, a line drawn from the balance center to the pallet center of a lever escapement; or, from the balance center to the escape wheel center of a chronometer or a cylinder escapement. The angular measurement of escapement action should be equal on both sides of the line of centers.
centigrade – Scale for thermometers in which the freezing point of water in zero (0°), the boiling point 100°, and the space between divided into 100 equal degrees. See FAHRENHEIT.
centimeter – One hundredth part of a meter or 10 millimeters.
Central Selling Organization – Abbreviated “C.S.O.”, diamond producers’ cooperative comprised of the Diamond Corporation, which buys from independent producers and holds reserve funds; the Diamond Trading Company, which sells gem and near-gem rough; and Industrial Distributors which sells bort and drilling diamonds. It conducts “sights” (sales) of gem quality at its London headquarters, 2 Charterhouse St., for some 220 invited customers. During quiet periods, it stockpiles rough to minimize short-term fluctuations and stabilize diamond prices.
centrifugal casting – A method of making small metal castings used in jewelry shops. Molds, filled with melted metal, are whirled by machinery so that centrifugal force crowds metal into the smallest spaces producing work sharp in details. Synonymous with LOST WAX CASTING.
centrifugal governor – A speed-regulating device in which a pivoted balance arm with weights acts against springs or gravity.
ceragate – (sir’a-gate) A wax-yellow colored chalcedony. See CARNELIAN and SARD.
ceramic resistor – An electrical resistor whose current-resisting elements are part of the ceramic mold.
cerkonier – (ser-kon’yer) Ceylonese term for colorless to pale straw-yellow zircon.
Certified Gemologist – A title granted by the American Gem Society to jeweler members who have completed several advance gemology courses and examinations.
Certified Master Watchmaker – One who has passed the examination for that grade of ability, offered to watch-makers by the American Watchmakers Institute. Less advanced grade of examination and certification by the Institute in that for Certified Watchmaker.
cerulene – (seer’u-leen) Little used trade name for an Australian calcite colored green and blue by malachite and azurite. This coloring is not uncommon, and cerulene is rarely used as a gem or decorative material.
Ceylon chrysolite – Misnomer for yellow-green tourmaline.
Ceylon cut – Mixed cut.
Ceylon diamond – Misnomer for colorless zircon.
Ceylon garnet – Almandine garnet from Ceylon, sometimes sold under the misnomer Kandy spinel.
Ceylon hyacinth – Misnomer for hessonite garnet.
Ceylon opal – Misnomer for moonstone.
Ceylon peridot – Misnomer for yellow-green tourmaline.
Ceylon ruby – Although they are often called pink sapphires by buyers, true rubies of a light pigeon-blood, pinkish red hue are found in Ceylon, in association with sapphires and a number of other stones. A bluish tinge in these stones can be intensified by heating and most Ceylon (Sir Lanka) “rubies” are treated on this fashion.
Ceylon sapphire – Usually taken in the trade to mean a somewhat paler blue sapphire than the Kashmir. The proportion of deep-colored Ceylon stones is smaller than the proportion in Siam, though the cornflower blue color does occur.
Ceylon shell – Margaretifera variety found near Ceylon, distinguished by a yellow color and a chocolate brown lip.
chain guard – In a fuzee watch or clock the attachment to keep the chain or cable from winding itself off the fuzee.
chain-wind – A colloquial term designating fuzee motive-power in a timepiece. See FUZEE.
chalcedony – (kal-sed’o-ny) 1. A microscopically crystalline variety of quartz forming in almost transparent to translucent masses; gray, white, blue, black, brown, etc. 2. Much chalcedony undergoes treatment. Upon heating, some white chalcedony becomes carnelian; upon dyeing, chalcedony can resemble black onyx, sard, or sardonyx so closely that detection is difficult or impossible, or imitate chrysophase or lapis-lazuli. See BLUE MOONSTONE; BLUE CHALCEDONY; BLUE CHRYSOPHASE; AZURLITE; CHRYSOPRASE; AGATE; CORNELIAN; SARD; CERAGATE; CORALLINE; CALIFORNIA MOONSTONE.
chalcedony moonstone – The clearest quality of chalcedony. See ORIENTAL CHALCEDONY.
calchihuitl – (chal’chi-hwee”tl) A Mexican term used somewhat indiscriminately for any stone which has been carved into a decoration or useful object. It usually refers to jadeite or turquoise, but sometimes to porphyry or serpentine. While no mane distinction is made, value differences are appreciated, with jade the most desirable material. (Also spelled chalchihuite.)
chalk – Carbonate of lime; used in block form for cleaning watch brushes, and in powdered from mixed with alcohol for cleaning watches.
chank pearl – The sacred pearl of the Hindus. A natural pink pearl found in the chank (Turdinella scolymas).
channel setting – A type of setting often used in mounting a number of small stones of uniform size in a row, as in diamond wedding ring. Instead of each stone being held by its individual set of prongs, a continuous strip of metal with a channel into which are fitted the outer edges of the row of stones runs down each side of the row, which is thus gripped between the two walls.
chapter ring – That part of a dial upon which the numerals are placed.
chapters – The numerals on a clock dial.
characteristic – Diamond clarity grading. A term used by the American Gem Society for inclusions and surface marks, the size, number and visibility of which affect the appearance or durability of the diamond. External characteristics include; cavity, nick, external grain, knot or twinning line, scratch or wheel mark, natural, rough or chipped girdle. Among internal characteristics are: feather, including crystal, black spot, pinpoint, cloud, knob, percussion mark or bruise, bearded or feathered girdle, and internal grain, knot or twinning line.
charcoal – Carbon made by charring wood in a closed chamber; used in block form by jewelers to support work being soldered; and by watch-makers to hold steel to heat it for hardening. For either purpose, charcoal made specially of willow wood, is preferable to ordinary fuel charcoal. In powdered form is used as a deoxydizing agent in melting metals.
charged lap – A polishing or abrasive lap whose surface has been embedded with polishing or abrasive powders.
chariot – The adjustable potence in a cylinder escapement housing the lower balance bearing.
charm – Miniature object with link for attachment to a chain bracelet. Charms depict flags, drums, violins, whistles, bugles, hearts, egg beaters, horseshoes and an endless variety of other subjects.
chasing – A highly skilled and ancient art of decorating metal with figures or ornamental patterns, which may be either raised or indented. The work is done entirely by hand without mechanical aids, only tools used being hand hammers and punches of various sizes and types. Chasing “flows” the metal into the desired decoration and thus differs from engraving away the metal. See EMBOSSING; REPOUSSE.
Chatham-Created Emeralds – Term descriptive of synthetic emeralds made by Carroll F. Chatham of San Francisco; its use was approved by the Federal Trade Commission on September 5, 1963. FTC found the term imputes “that this product is not a creation for nature that it is man-made, and that it is artificial or synthetic.
chaton – (sha-tawn’) 1. Or chaton foil, a foil-backed glass gem. Also the gem part pf a ring setting. 2. In watches, the bushing into which in set a jewel.
chatoyancy – (sha-twah’yan-sy) The single line reflection of cat’s-eye gems. See CAT’S-EYE; ASTERISM.
chatoyant malachite – (sha-twah’yawn” mall’a-kite) Malachite with a cat’s-eye effect. A not uncommon phenomenon, as the green copper carbonate often forms in fibrous masses.
chatoyant obsidian – An unusually gray variety of obsidian with parallel cavities or inclusions which, when properly cut, give a fine cat’s-eye. Found in loose pebbles in New Mexico and probably elsewhere. See PERLITE.
cheesehead screw – Horological screw with straight cylindrical sides and flat top.
chemical clock – A chemical cartridge used to check duration of electrical rate of current consumption, indicated on a scale.
cherry opal – Translucent red opal produced in Nevada and Mexico. See FIRE OPAL.
chert – (churt) 1. A light-colored compact opaque variety of quartz, widely used by the Indians in arrow heads and may be the material which is dyed blue for so-called Swiss lapis. 2. In finely divided form is used as an ingredient of Tripoli. See TRIPOLL.
chessylite – Azurite, a European name derived from the French copper-mining locality, Chessy.
chevet or chevee – (shev-ay’) A flat gem with a polished concave depression in which there may be a raised design. A cameo with a raised border higher that the cameo proper. See CUVETTE, CURVETTE.
chevron – 1. A simple form of ornament consisting of short lines joining at angles. 2. A hallmark of three chevrons is stamped on many Swiss watch cases made prior to 1880.
chiastolite – (ki-ast’o-lite) A variety of andalusite which forms crystals which reveal, when sectioned, a light-colored cross or other regular design in a black ground mass. Synonyms are cross stone, hole spar, lapis crucifer, and stealite. See ANDALUSITE.
Chicot pearl – Blister pearl.
Chilean lapis – A locality name for a type of lapis lazuli characterized by a pale color and much matrix.
chime clock – A striking clock in which the hourly quarters are indicated by melodies played on bells or gongs; differentiated from striking clocks in that the latter indicate time units and fractions instead of melodies.
china opal – Common opal resembling china in appearance.
china pearl – A pearl with two drilled holes.
Chinese amber – Usually German pressed amber or bakelite; rarely does it refer to Burmese amber, which might be considered a proper usage. See BURMITE.
Chinese duplex – A Swiss watch made of the Eastern trade employing a duplex escapement whose teeth tips were notched to permit an apparent full-seconds jump to the central seconds hand at every alternate cycle of the balance.
Chinese jade – True jade or jadeite.
Chinese nephrite – Nephrite jade, as distinguished from jadeite jade.
Chinese ruby – Misnomer for purplish-red stones, obtained by heating rock crystal, then plunging it into a cold liquid dye, followed by a paraffin bath to diminish the crackled appearance.
Chinese tourmaline – In reality, a misnomer Carved Chinese tourmaline objects are made mostly of California tourmaline, or more recently of tourmalines from other localities, but not from China.
Chinese turquoise – Misnomer for an artificially colored substance made to resemble turquoise. The Chinese have carved much real turquoise as well.
Chinese white – Oxide of zinc; used in cake or paste form for coating gold, silver, etc., with a white surface on which engravers draw designs for engraving. Also used by jewelry designers for water-color pictures of new designs.
chip – 1. a. Diamond cleavage fragment of small size, less then one carat. b. A type of surface damage, often square or hexagonal, on the girdle or a facet edge of a cur stone. c. A common misnomer for a small diamonds. 2. A classification in sorting rough melee-broken or irregular crystal weighing less than a carat or less than half a carat. 3. Horol. A nickname for an integrated circuit; technically, one that is unpackaged. See INTEGRATED CIRCUIT.
chlorastrolite – (klor-as’tro-lite) A fibrous, light bluish-green variety of prehnite, which, when cut, shows a cat’s-eye effect. Pebbles of this material are found on the shores of Isle Royale, Lake Superior, and are sometimes cut as gemstones. Hardness, 5-6; specific gravity, 3.2; designated the official state gem of Michigan in 1972.
chlorethane – A non-flammable hydrocarbon used as a degreaser in clock cleaning.
chlorides – Combinations of the element chlorine with other elements. Particulary in the jewelry trade, the chlorides of gold, silver, and platinum are used as salts for making electroplating bathes, etc.
chloromelanite – Opaque, green Burmese jadeite, often with black specks and somewhat resembling, because of its opacity, malachite. In part it may also be a substance known locally as maw sit sit, which appears to be largely a fine-grained quartz-feldspar mixture saturated with microscope flecks of an uncertain green material.
chloropal – (klor-oh’pal) In correct usage, a hydrated silicate of iron and not a gem mineral. The name has been mentioned erroneously in connection with a greenish common opal from Silesia. See CHRYSOPAL.
chlorophane – (klor-oh-fane”) A variety of fluorite which phosphoresces green under mild heating. Erroneously used in connection with any gem variety, for, though the fluorite may posses the property, the owner of a cut stone in unlikely to observe it. Most fluorite phosphoresces in this way.
choke – A short, 14-in. necklace, just long enough to go around the throat. Usually applies to a string of pearls or beads.
chops – 1. On pendulum suspension springs, short metal blocks embracing upper end of spring, to rest on pendulum hanger. 2. Parts of pendulum hanger on each side of the slot in which the suspension spring hangs.
christal – An old name for mother of pearl used in inlays.
chrome diopside – Chromiferous, emerald-green diopside, now finding some use as a gemstone. Known from Tanzania, Brazil, and the USSR, but infrequently seen in jewelry.
chrome garnet – Uvarovite garnet.
chrome kyanite – A green variety of kyanite with 1.81% Cr2 O3 found at Yakutia, Siberia. Its high and low refractive indices are 1.734 and 1,718.
chrome mica – Fuchsite.
chrome tourmaline – Recently discovered chromium-bearing tourmaline found in a locality, not far from the Longido Hills, Tanzanian zoisite locality, and associated with emerald green to colorless grossular garnet.
chromism – Liquid crystal displays of various colors.
chromium – An elemental metal used for electroplating, principally on cheap quality watch cases, bracelets, etc. Chromium is also used as an alloy in special steels such as stainless steel and is sometimes used in dies for manufacturing jewelry. Chromium is important from a gemological standpoint because minor amounts color emeralds green and rubies red. See ALLOCHROMATIC.
chromojadeite – (krome’o-jade”ite) Tawmawite, maw sit sit, chloromelanite.
chronodrometer – Early Waltham watch with centered seconds and offset hour and minute hands.
chronograph – (kronn’o-graff) 1. An instrument used for recording time signals on a paper-covered rotating cylinder. 2. A watch with center-seconds hands which may be started at zero, stopped to record the time of an event, then returned to zero by operating a button on outside of watch case, besides the ordinary hour and minute hands. See CENTER SECONDS; SPLIT SECONDS.
chronometer – (kroe-nomm’e-ter) Broadly speaking, an instrument for measuring time, but customarily used as meaning as accurate portable timepiece with detent escapement, beating half seconds, and used for navigation or other purposes requiring an extremely accurate portable timepiece. See MARINE CHRONOMETER.
Chronos – The Greek god of time. Father Time.
chronoscope – Timepiece showing time intervals. The correct term for a chronograph.
chrysoberyl – (kriss”oh-bear’il) An important gem mineral, a beryllium aluminum oxide. In addition to the ordinary yellow-green transparent gem, best known simply as chrysoberyl, there in also a yellow-brown golden variety as well as the two more valuable gems, alexandrite and cat’s eye. See CEYLON CAT’S-EYE: SCHILLER CHRYSOLITE; CYMOPHANE.
chrysocolla – (kriss’o-koll”a) A hydrous silicate of copper, not hard enough for use as a gem alone, but frequently coloring quartz and making an attractive stone. See BLUE CHALCEDONY.
chrysolite – (kriss’oh-lite) A much abused word. Chrysolite, properly speaking, is a variety of olivine, a magnesium iron silicate common in igneous rocks and ranging from light yellow-green in color through brown and gray. Clear gemmy crystals are found on St. John’s Island in the Red Sea, as well as elsewhere, and the cut gem of this material is properly known as peridot. Its use as a modifier, such as chrysolite chrysoberyl, is permissible, but tends to be misleading, and is therefore undesirable; yellow-green chrysoberyl and spinel are preferable terms. Chrysolite has many other meanings as well. It has been applied to aventurine glass. Bohemian chrysolite, pseudo-chrysolite, false chrysolite, and water chrysolite are all moldavite; Brazilian chrysolite is chrysoberyl or tourmaline; Oriantal chrysolite is corundum or chrysoberyl. Ceylon chrysolite is tourmaline; Saxon chrysolite is precious topaz; Cape chrysolite is prehite; schiller or opalescent chrysolite is chrysoberyl as is chrysolire chrysoberyl; aquamarine chrysolite is a yellow-green beryl; Siberian chrysolite or olivine, or Uralian olivine is demantoid garnet. Evening emerald is chrysolite or peridot. See FORSTERITE, HAWAIITE.
chrysolithus – (kriss’oh-lith-us) Misleading name for yellow-green beryl. Also Pliny’s name for golden sapphire (Indian c.) and zircon (Arabian c.).
chrysopal – (kriss’oh-pal) A translucent, nickel colored green common opal, which occurs in Silesia with chrysoprase.
chrysoprase – (kriss’oh-praze) A translucent apple-green colored variety of chalcedony which derives its color from a small percentage of included hydrous nickel silicate.
chuck – A work-holding device used in lathes consisting of a steel cylindrical piece with slits radiating from a hold to form spring-jaws to clamp the work. See COLLET.
Cico pearl – Misnomer for imitation pearl.
cinnabar – (sin’na-bar) The only ore of mercury, a red compound of mercury and sulphur. Some chalcedony is red or streaked with red because of the presence of cinnabar. Cinnabar is used as a coloring material by the Chinese for their red lacquers.
cinnabar matrix – A Mexican quartz with bright red cinnabar inclusions.
cinnamon stone – Hessonite garnet, the name being derived from a similarity in color between the stone and cinnamon bark.
cinnamite – Cinnamon stone.
cipher – A monogram, usually of two or more letters intertwined or superimposed, to form a pleasing design. See ENGRAVING.
circle agate – An agate with circular stripes.
circuit – In electrical timepieces, that path through which electrical impulses travel.
circuit, integrated – The compact electrical unit of a timepiece utilizing transistors, diodes, capacitors and resistors.
circuit, short – Excessive current caused by accidental contact across the electrical system.
circular error – An error in the timekeeping of a pendulum due to its varying arc of motion, which may be minimized by designing escapements enabling short arcs of pendulum motion.
circular pallet – One of the design-types of lever escapement pallets, in which a circle struck from pallet center passes though the centers of lifting faces of both pallet stones. This type escapement has unequal unlocking resistances on the two pallets, but equal lifting leverage effects. It was used mainly in American-made watches. See EQUI-DISTANT PALLET, ESCAPEMENT.
circular pitch – A measurement on the pinch-circle of a gear wheel or pinion; a unit of circular pitch is equal to the circumference of the circle divided by the number of teeth or leaves. See ADDENDUM: CENTERDISTANCE: PITCH-CIRCLE.
Certification (or Diamond Grading Reports) – There are many recognized gemological laboratories that can grade your stones for a fee. The most well known is the GIA, Gemological Institute of America.
citrine – (sit’rin) A yellow to brownish quartz variety of quartz. Almost all so-called topaz in the trade is actually citrine quartz; in such cases, use of the word topaz without the word quartz is an unfair trade practice. See BOHEMIAN, COLORADO, OCCIDENTAL, SCOTTICH, SPANISH TOPAZ; TOPAZ QUARTZ.
clamp – One of the prongs or fingers of metal belonging in setting for a gemstone, with its top formed to support and hold the stone at its edge or girdle. Synonyms: claw, cramp.
clam pearl – Name usually given pearls found in clams and oysters which lack the sheen necessary to a precious pearl. Also used erroneously for the pearls of the fresh water mussel.
clam-shell imager – A stone-melting device consisting of two parabolic mirrors set to create an external image at a focal point just behind one of the mirrors. They have been used for the melting of high-melting-point materials and may find some use in gemstone synthesis.
clarity – In diamond grading, the incidence of inclusions and surface blemishes; one of the so-called “four C’s” by which diamonds value is measured. Some diamonds reveal no inclusions or surface blemishes when examined under the highest feasible degree of magnification; others are almost opaque to the unaided eye. See INCLUSIONS; SURFACE BLEMISHES; CLARITY GRADE.
clarity grade – The relation purity of a cut diamond; its position on a flawless to imperfect scale, determined as the American Gem Society say, “not only by the size, number and visibility of inclusions and surface marks, but also by their nature, location, and effect on the durability of the diamond.” A number of clarity grading systems are used by manufactures, imposters and retailers in the U.S. and overseas, several of which are shown in the adjustment table. Precise comparison among system are impossible because of their varying requirements. b. Colored stones. Clarity grading standard for colored stones are: “clear to the unaided eye” (C), “lightly included” (LI), “moderately included” (MI), “heavily included” (HI), and “excessively included” (EI).
clasp – An attachment used to connect the two ends of a neck chain or similar piece of jewelry. Clasp are made in a great variety of forms, and types as to fastening mechanism; some of them are really fine pieces of jewelry, decorated and set with gems.
clatersal – Diamond cleavage fragments suitable only for crushing.
clean – An ambiguous diamond-grading term; understood by some jewelers to mean absence of inclusions, by others to mean slightly included. Members of the American Gem Society may not use the words “perfect” or “clean” in diamond description.
cleaning – Horology. Removal of thickened oil, dirt, etc., from watch and clock mechanisms, to be followed by fresh oiling. Cleaning is made necessary more by evaporation and thickening of oil, than by foreign dirt – a fact it is well to emphasize to watchmakers’ customers, who are apt to question even a reasonable frequency of need for cleaning, if cases are tight and exclude dirt. Cleaning is done by various processes, using either hand brush, or machines in which ultrasonic agitation or whirling the watch parts in solution. Jewelry is now cleaned ultrasonically. See ULTRASONIC.
clear amber – Transparent amber, ranging in color from water white, through yellow, orange and orange-red to deep brown.
cleavage – 1. A property possessed by many crystallized substance of breaking readily along certain planes, with a resultant flat surface. Different minerals have different cleavages, their directions depend upon their internal molecular structures. Diamonds cleave parallel to the octahedral faces, so does fluorite. Topaz cleaves parallel to the base, kunzite normal to the base, and hence, normal to the table as it is usually cut. 2. A diamond classification term for medium-sized cleavage fragments. See BLOC; CHIPS. 3. A separation parallel to an octahedron face of the original crystal, undesirable because it is a break with danger of extension. Many diamonds are found with cleavages already present; other cleavages develop during cutting or wear. A cleavage, viewed end on, resembles a single straight line; viewed at right angles, a feather. See FRACTURE.
Cleavage – A natural area of the diamond where a weak bond holds the atoms together. The gem will be split along these planes by the cutter.
cleaving – A process used in the fashioning of diamonds especially, breaking the stone into two or more pieces to make it a better shape and size, or to bring flaws to a surface, from which they may be cut without too great loss of material. Any other gem or mineral posses-sing a cleavage may be cleaved, of course, but in gems it is widely used only in diamonds. Cleavage is of great value in the commercial utilization of mica, for an additional example.
clepsydra – (klepp’si-drah) An early form of timepiece in which water, slowly escaping, and gradually reducing its level, provided a crude measurement of time.
click – An adjustment of a toothed ratchet wheel, with a point that enters between teeth and prevents background movement of the wheel; used in winding mechanism of timepiece. See RECOILING CLICK.
clicking – The rapid action of an escapement due to failure of the locking action.
click-spring – Spring pressing on a click to keep it in place in the teeth of a ratchet wheel.
clip – A piece of jewelry of the same general style as a brooch, but with a spring clip fastening on the back instead of a pin and catch.
clock – A timepiece used normally in stationary position, not worn on the person. The word is derived from the medieval Latin meaning “bell”; the earliest clock struck time on bells, only; dials and hands were a later development.
clock, secondary – A slave clock with only a dial train, obtaining its impulses from a master clock.
clockwise – Moving in the same direction as the hands of a clock-from left to right, looking at the top of the path of motion.
close goods – Rough diamond crystals of regular shape.
close plating – An early plating process that is now obsolete. The surface to be coated was cleaned, fluxed and tinned and a thin foil of silver was then affixed thereto by pressure and by the aid of silver of a hot soldering iron.
close set – Brilliants in a setting with a solid back, in contrast to open set or “à jour.”
closing – 1. Designates contracting diameters of worn pivot holes with a punch-quick, cheap expendient inferior in mechanical effectiveness to bushing. See BUSHING. 2. Contracting diameter of seat for mainspring barrel cover, to correct loose fit, done with barrel closing punch and die.
cloud – A white, cottony inclusion area within a diamond, made up of myriads of submicroscopic gas-filled spaces; often has the regular shape of a crystal.
cloudy agate – Chalcedony type agate, with more and less transparent areas; a term used to emphasize a contrast with banded agate.
cloudy amber – Translucent, semi-translucent and opaque amber, ranging in color from pale yellow to dark brown.
club tooth – A form of escape wheel tooth in the lever escapement, in which the end of a tooth is a short plane which shares the total lifting action of the escapement with the lifting face of the pallet stone. This is the prevailing tooth form, displacing the earlier pointed or ratchet tooth characteristic of old English watches.
Cluster setting – This setting surrounds a larger center stone with several smaller stones. It is designed to create a beautiful larger ring from many smaller stones.
clutch – 1. In jewelry a device which locks onto the pin of a tie-tac, brooch or scarf-pin to prevent loss. 2. A device, in a stem-wind watch, to shift power from the stern to either the winding or setting gearing.
clutch pinion – The cylindrical-necked steel pinion in a watch-setting mechanism with slanted ratchet teeth which can be shifted from the winding to the setting phase.
coarse mêlée – Small diamonds running 6 to 10 to the carat.
cobalt – A silver-white metal, harder and stronger than iron or nickel. Used as an alloy in the making of steel and as a coloring material for many blue glasses which simulate gems.
cobaltite – A cobalt arsenic sulphide resembling pyrite though somewhat pinker, and some-times but as a gem. It is an ore of cobalt.
cobweb matrix – Turquoise with an interesting network of fine blue lines.
cock – A part of the framework of a timepiece holding a bearing for a pivot, with a base at only one end where it is fastened to another part of the framework. See BRIDGE.
cock beading – Small convex or half-rounded molding.
cocktail ring – A finger ring of three-dimensional design, usually combining small diamonds and small colored stones with gold or platinum. Also called a bridge ring.
cocoanut – Popular term for the very hallow, round geodes from northern Mexico, the drusy crystal of which are often amethyst. See GEODE; DRUSE.
coconut pearl – 1. Singapore name for natural pearls. 2. Round concretions found in cocoanuts, of no value but confused by tourists with the giant dull Tridacna pearls.
Coddington magnifier – An optical lens, conveniently mounted, used largely for inspecting diamonds and other gem stones. The magnifying powers may be had in strengths from 7 to 20 diameters.
coded-price catalog – A direct-mail catalog containing a coded or “hidden price” adjacent to a purported retail price; for example 121CD1204…$17.95. In this instance, as explained elsewhere in the catalog, 121CD is the catalog stock number, 1204 reveals “your cost,” $12.04; and the “suggested retail price” in $17.95.
coefficient of expansion – Horology. A figure stated as a multiplier of another figure; for example, the coefficient of expansion of steel is 0.0000073 per degree centigrade; brass has a higher coefficient; the difference in these coefficients is the reason for choosing steel and brass for making bimetallic compensating balances. See COMPENSATING BALANCE, COUNTER-ENAMELING.
cog – In gearing, a wheel tooth or a pinion leaf.
coil assembly – All the units associated with a electromagnetic coil in a timepiece.
coil block – The platform or body upon which the coil assembly is mounted.
coil, dual purpose – In transistorized timepieces, a coil wound within or with another; one serving as the phase-sensing coil, the other as the impulsing coil.
coils – A term used specifically in referring to the main body of spiral coils below the overcoil of a Breguet hairspring.
coin – This word was die-stamped on much American silverware between 1837 and 1868. It indicated that the metal was of the same fineness as American silver money, which was 900 parts pure silver and 100 parts copper. The fineness was sometimes indicated by the letter C (coin) or D (dollar). IN 1868, the Gorham Company adopted the English standard of Sterling (925/1000) and other silversmiths followed suit.
coin gold – United States gold coins were made of an alloy of nine parts pure gold and one part copper.
coin jewelry – 1. a. Coins, mounted in any manner, and worn for adornment; long popular in many parts of the world, especially as women’s necklace. b. In the U.S., a vogue after 1950 for coins mounted in charms spread subsequently into all types of jewelry, mounted with U.S. and foreign gold and silver coins, for both women and men. 2. Federal law prohibits the alteration or mutilation of U.S. coins with fraudulent intent, but does not restrict the manufacture of jewelry or novelty items by cutting, soldering or gold-plating coins.
coin silver – Silver assaying 900 parts pure silver to every 1000 parts. U.S. coins were made of this quality, which is 25 points lower than sterling standard.
coin watch – A watch movement encased within a coin.
collector – One of the three parts of a transistor, the other being the emitter and the base.
collet – (koll’ett) 1. Jewelry. a. A band or collar used decoratively and made with the top and bottom edge parallel. b. A flange in which a gemstone is set. c. Same as culet. 2. Horol. A split ring of bass holding the inner terminal of the hairspring, which is pinned to it, to a balance staff. b. Machinists’ term for a spring-jawed lathe chuck.
collimator – Horol. A device which, like the lens of a telescope, acts electronically to collect emissions from a radioisotope and cause them to pass in a parallel manner through a counter. See NUCLEAR WATCH.
colloidal – An element composed of microscopic particles such as graphite and used to grease watch and clock parts.
Colombian emerald – An emerald from Colombia, the locality for the finest emeralds and often used without regard to the true source to signify a good quality stone.
colophonite – Applied variously to a brown garnet and to a brown variety of vesuvianite from Arendal, Norway.
color grade – The classification of body color of cut diamonds, ranging from colorless to yellow. Comparable color grades are not used for other hues, which are called fancy. Many different color-grading systems are used by cutters, dealers and retailers in the U.S. and overseas, several of which are shown in the adjacent table. Precise comparisons are im-possible, due to the varying requirements of the several systems. See COLORIMETER, DIAMONDLITE, KOLORISCOP.
colored stone – By trade usage, any gemstone except diamond, including colorless varieties, such as white sapphire or white topaz. But it does not include diamonds of color.
Colored Stone Certificate – Award from Gemological Institute of America for completion of its correspondence or residence courses on colored stones and gem identification.
colorimeter – An instrument that gives a numerical or alphabetic result when sued to obtain a color reading.
colorless – Free of any color; preferable in a diamond description to the old, but inaccurate, blue-white.
Colorado goldstone – Trade name under which brown aventurine glass is sold in Colorado. See AVENTURINE.
Colorado ruby – Misnomer for pyrope garnet.
Colorado topaz – Misnomer for citrine or smoky quartz. However, real colorless and blue topaz is found in Colorado.
coloring – A surface finish given to pieces made of precious metals, usually comprising an electroplating with pure metal such as 24 karat gold, on goods made of lower karat gold; or a chemical treatment that absorbs alloy from the surface of the metal, leaving the surface as a thin film of purer metal.
column wheel – The castle wheel of a chronograph with radial, ratchet teeth and perpendicular abutments used to phase the levers.
commercially clean – An early diamond-grading term meaning, ambiguously, “reasonably free from inclusions.” The Federal Trade Commission forbids its misuse with intent or capacity to deceive; the American Gem Society forbids its use altogether.
commercially perfect – An early, often misleading, term suggesting that a diamond is nearly perfect. The Federal Trade Commission forbids its use for a stone that is not perfect by FTC definition; the American Gem Society forbids its use.
commercial standard – Voluntary recorded standards, promulgated by the National Bureau of Standards, agreed upon by producers, distributors, and consumers, covering terminology, types, classification, grades, sizes, and use characteristics of manufactured products as a basis for better understanding between buyer and seller. They include standard methods of test, rating, certification, and labeling, and provide a uniform basis for fair competition. They are made effective by means of voluntary guarantees on invoices, on labels, or grade marks on the goods themselves.
commercial white – Misleading term sometimes applied to common white diamonds with slight yellow tint. The Federal Trade Commission condemns its use. Such diamonds could be crystal, top cape or even cape.
common opal – The name given to hydrous amorphous silica, opal, which does not have the fire and play of color characteristic of gem precious opal. Common opal is frequent and some forms find gem use because of the attractive coloring sometimes caused by impurities. See CHLOROPAL; CHRYSOPAL; MENILITE; CACHOLOG; HYALITE; HYDROPHANE; CHINA OPAL; FIRE OPAL.
commutator – That part of a motor against which the brush rubs to transmit electrical energy. Also used to change direction of a current.
compensating balance – A balance with rim in two segment made of steel inside and brass outside. When an increase of atmospheric heat causes a slower timing rate in the hairspring, the same heat bends the bimetallic segments inward, making the balance smaller, therefore faster in its timing rate, sufficiently to offset the slowed rate of the hairspring – and vice a versa when the atmosphere becomes colder. The bending of the segments is due to the difference in the coefficients of expansion of the steel and brass in them Adjustment to temperature comprises trying balance screws in various positions on the rim segments, during timing tests of the watch in oven and refrigerator, so as to vary the compensating effects, until these are as nearly as possible made to offset temperature effects on the hairspring. See BALANCE; COEFFICIENT; ADJUSTMENT.
compensation – 1. Horol. Provision for making the timekeeping of balances or pendulum uniform during changes of atmosphere temperature in heat and cold. See BALANCE; CURB; PENDULUM. 2. Jewelry making. Making a model oversize to compensate for shrinkage of casting. See MODEL MAKER.
complimentary metal-oxide semi-conductor – A type of integrated circuit used in many quartz watches.
compound pendulum – An assembly of parts comprising a bob, rod, and suspension, the actual pendulum of a clock; differentiating from the corresponding “simple” pendulum which is an ideal, theoretical conception of the pendulum, not strictly realizable in physical form. See PENDULUM.
compteur – (kawn-terr’) Swiss name for a watch with center-seconds hand with chronograph action, but without ordinary hour and minute hands. See CHRONOGRAPH; RATTRAPANTE.
comptonite – An opaque variety of the zeolite, thomsonite, which occurs in mydaloidal (gas in lava) cavities at Good Harbor Bay, Lake Superior. It has a radiating banded structure, white, yellow, and green, and washes out of the rocks as pebbles which may be picked up on the beach. It is often cut into attractive cabochon gems. See LINTONITE; THOMSONITE; CHLORASTROLITE.
concave – Curved inwards.
concentric – Two or more things having the same center; for example in the balance-assembly of a watch, the staff, roller table, hairspring, and balance are concentric.
conchiolin – (kon-ki’o-lin) The nitrogenous organic substance in shells and pearls which cements the calcite and aragonite which are the principal ingredients.
conch pearl – (konk) A pearl found in the great marine conch snail. It is usually pink in color but never lustrous like a precious pearl.
conch shell – Shell of the conch snail, used in making shell cameos.
concussion mark – Diamond grading. A small bruise, usually outlined by minute cleavages in a four- or six-sided pattern, commonly found on most diamonds after wear.
conductance – The ability of an object to transmit an electrical current.
Confédération Internaltionale de la Bijouterie, Joaillerie, Orfèvrerie, des Diamants, Perles et Pierres – Usually abbreviated CIBJO, this is the International Confederation of Jewelry, Silverware, Diamonds, Pearls, and Stones, formed in 1961 by trade groups from Austria, Belgium, Denmark, France, Federal Republic of Germany, Great Britain, Italy, Netherlands, Spain and Sweden; joined soon after by trade groups of Finland, Israel, Norway, Switzerland and the U.S. Purpose: to harmonize definitions and practices.
Congo emerald – Dioptase.
conical pivots – Pivots used in bearings with cap-jewels, on balance staffs and other arbors moving at high speeds with light pressures. Also called conoidal pivots.
Congreve clock – A clock whose regulating frequency is governed by the speed of a rolling ball in grooves on an incline plane which reverses its angle at the end ‘run’.
conoscope – (kon’o-skope) An instrument for the examination of gems in convergent polarized light, which gives interference figures.
constant force escapement – Escapement in which the equal power supplied to the escapement is not directly dependent on the mainspring.
continuity tests – Tests of electrical timepieces to discover breaks in a current flow.
counter-clockwise – Moving in a direction contrary to the motion of clock hands; from right to left, viewed above the center of motion.
contrate wheel – A gear wheel with teeth standing at right-angles to the plane of the wheel. See CROWN WHEEL.
controle-mark – A mark stamped by a municipal bureau of Geneva, Switzerland, (Bureau pour le Controle Facultatif des Montes de Genève) on watches of high quality, as proof of Geneva origin and quality; one of the measures taken to maintain the reputation of Genava-made watches.
copal – (koe’pul) A light-colored natural resin resembling amber. It can be distinguished by its lighter weight, it floats in a salt solution in which amber is balanced.
copper – A reddish metallic element, used in the pure form as a conductor of electricity, also in enamel dial bases and dial feet, as an alloying element in sterling silver, karat golds, brasses bell metals, bronzes, and other alloys. Melting point 1083°C.; specific gravity 8.9; chemical symbol Cu.
copper bracelet – Bracelet or band made of copper; said to cure or ward off arthritis, bursitis and rheumatism; the wearing of such bracelet became “the latest fashion accessory” in 1969, with Rudolph Nureyev, Pierre Cardin, Lauren Bacall and Vince Lombardi joining “the green wrist mania.”
copper mica – A misnomer for green mica such as that which makes quartz aventurine. It is actually a chromium-colored mica.
coque-de-perle – 1. Natural hollow pearl. 2. Oval section of pearl shell, round and polished to imitate a blister pearl. Often cut from the shell of an Indian nautilus.
coral – The hard calcium carbonate external skeleton of the coral animal. Many individuals build up stony masses of this material which is often cut as a gemstone. The oxblood red color (arciscuro or carbonatto) is mostly valuable. It also comes in white (blanco), pink, cream-color, pale flesh pink (pelle d’angelo), pale rose (rosa vivo), salmon color (secondo coloro), red (rosso) and dark red (rosso scuro), yellow, brown, blue, violet and black. See ACCARBAAR, BEEKITE, BOKE, BLACK CORAL, BLOOD CORAL.
coral agate – Agate with a coral-like design or a variety of fossilized coral, altered to quartz.
coralline – Red-dyed chalcedony.
corindite – An artificial abrasive consisting mainly of synthetic corundum.
Corinthian column – In clockwork, the fluted slender columns topped by a splayed, florid capital.
cornelian – Carnelian.
corner facets – Related to the corners of the octahedron from which the round diamonds was cut; top corner same as quoin facets; bottom corner same as pavilion facets. See BRILLANT.
corner pieces – The spandrels in a clock.
Cornish diamond – Misnomer for rock crystal quartz.
Corsican green – A bastite-like material, serpentine replacing a mineral with schiller colors, used in small curved objects.
corundolite – Misleading name for synthetic white spinal.
corundum – (koe-run’dum) The mineral of which ruby and sapphire are varieties. It is aluminum oxide, a naturally white compound, which is colored by impurities. Very few pieces of corundum, which is a relatively common mineral, have the clarity or beauty of color necessary for a gem stone. Common corundum is a constituent of emery and is useful as an abrasive. See ADAMANTIVE SPAR; RUBY; SAPPHIRE; ORIENTAL AMETHYST; ORIENTAL TOPAZ; ORIENTAL CHRYSOLITE; PADPARADCHA; SYNTHETIC CORUNDUM. Red synthetic corundum (synthetic ruby) is generally used for watch jewels. See JEWELED WATCHES, JEWELING.
costume jewelry – Women’s jewelry, moderately priced, highly styled and with fashion appeal, made from practically all materials.
cotterite – Cornwall term for Cornish quartz with a pearly, metallic luster which is caused by inclusions of colloidal, white clay.
count – Same as “trains.” The number of beats per hour to be made by balances or pendulums, to conform with the ratio of turns between the first and last wheels in trains, as: “18,000 trains” for which a balance assembly must be fitted that will beat 18,000 times per hour. See TRAIN.
counter-enameling – Enameling both sides of a piece in order to minimize distortion and cracking due to uneven expansion and contraction. See ENAMEL.
countersink – 1. A recess at the end of a hole, for example, a recess to accommodate the head of a screw. 2. A tool for countersinking.
counterweight – Extension on tower clock hands, or on poised pallets to balance the weight on opposite side of center.
count wheel – In a striking g clock, a wheel with sets of notches, from 1 to 12, into one of which a steel finger enters at each hour, the number of notches in the set governing the number of strokes. A deeper notch at the end of each set allows the finger to enter deeper to stop the striking mechanism for that hour.
coupling clutch – A chronograph lever with mounted wheel shifted to engage or disengage the chronograph device.
cover (barrel) – A metal disc fitting the groove in top barrel wall, with a hole in center to form a bearing for one of the barrel arbor shoulder pivots on which a going-barrel turns. See BARREL; BARREL ARBOR.
covered ratchet – Watch movement with a barrel bridge covering the ratchet, obviating a ratchet screw.
CPS – Cycles per second (HZ).
crab-claw escapement – Duplex escapement whose tooth tips resemble lobster or crab claws. See CHINESE DUPLEX.
crank roller – Impulse roller whose vertical jewel-pin is set into a crank-like roller c-1830.
craquelées – (krah-kell-ay’) Rock crystal gems which have been artificially “crackled” by heating. The iridescence derived in this way is negligible, but such stones are very susceptible to dyeing and most are so treated. See RUBASSE.
created – Term substituted for man-made or synthetic to describe laboratory-grown crystallized substance used in jewelry. First used by Carroll Chatham as an alternative for the FTC-disapproved “cultured,” as in “Chatham created emeralds,” it was taken up by other producers to combat a prejudice against “synthetic,” a term thought objectionable from its frequent misuse in description of all types of imitations, some of which were only glass.
cremaillere – The winding rack of repeating watches.
creolite – Red and white banded jasper found in California.
crepe finish – A dulled surface finish given to black hard enamel on jewelry by exposing the enamel to hydrofluoric acid or its fumes.
crescent – In horology, a semi-circular notch in edge of roller table of a watch movement to permit the guard pin or point to pass the line of centers during unlocking and impulse – sometimes called passing-hollow.
Cristaria plicata – Pearl-bearing fresh-water mussel of Chine and Lake Biwa, Japan.
critical angle – When used in relation to gems it means that angle beyond which all incident light is reflected, without escaping from the stone. The angle is dependent upon the index of refraction of the gem; the higher the index, the smaller the critical angle and more brilliant the gem.
crocidolite – (kro-sid’o-lite) An asbestos-like amphibole, blue in color. Of gemological interest because its structure is preserved in quartz replacements and the former fibers give the sheen and eye in the tiger eye.
crocus – (kroe’kuss) The coarser grains of oxide of iron, used for grinding metal prior to polishing; the finest grains of this material are called rouge.
crocus cloth – An abrasive material made by gluing crocus powder on smooth-surface cotton cloth.
cross-curved – Mainsprings which resemble the figure S in an unwound state and whose cross section in slightly bowed.
cross-filling – In metal work an operation for flattening work with files, consisting of filing diagonal strokes across the surface; then strokes at right angles to those first filed, showing the high spots of the surface, enabling these to be reduced to produced a flat surface.
cross-grained stones – Irregularly shaped and inter-grown diamond crystals.
cross rose – A modified 24-facet rose cut with 8 trapezohedral and 8 rhombohedral facets.
crossing – The formation of arms or spokes in wheel in timepiece trains.
crossing file – A file made of special form for forming curved-profile arms in train wheels. A double half-round file with different curves on each side.
crotch – In a clock, the fork on the pallet-lever that embraces the pendulum rod to connect it with the escapement through which impulse is given to the pendulum. Sometimes spelled crutch.
crown – 1. Horology. The milled or knurled button outside a watch case by which the watch mainspring in wound. 2. Gemology. Upper part of a gem. In a round brilliant cut diamond, the height of the crown, ideally, is equivalent to 16.2% of the diameter of the girdle, according to proportion calculated by Tolkowsky, approved by the American Gem Society, and sometimes called ideal or American cut. The ideal crown height in 14.6% of the diameter of the girdle, according to standard adapted in 1970 by Scandinavian jewelers, and sometimes termed European cut.
Crown Angle – relationship of the crown to the girdle; measured in degrees.
crown glass – A calcium, potassium or sodium, silicate glass commonly used in imitation gems. The refractive index lies between 1.44 and 1.53, the specific gravity from 2.05 to 2.60.
crown-wheel – 1. The escape-wheel of a verge escapement. 2. A contrate wheel in stem-wind work in watches. See CONTRATE WHEEL. 3. The wheel connecting the stem winding pinion to the ratchet wheel.
crucible – A container made of refractory material in which metals are melted. They are made in sizes and shapes to suit the purposes to which they are put.
crucible furnace – A furnace for melting quantities of metal in crucibles.
crucite – (krew’-site) Andalusite, variety of chiastolite.
crushing bort – A redundancy but perhaps service-able for greater emphasis on the worthlessness of the material for any use but diamond dust. See BORT.
cryptocrystalline – (krip’ to-kriss”tal-leen) Term for microscopically crystalline. Agate and chalcedony are best known examples of this structure.
crystal – 1. Gemology. A naturally angular shape, bounded by plane surfaces which are related to the internal molecular structure. They possess certain elements of symmetry and are grouped into six systems based upon these elements. See CUBIC; TETRAGONAL; HEXAGONAL; ORTHOHOMBIC; MONOCLINIC; TRICLINIC; also AMORPHOUS. In diamond grading, the most perfect octahedrons of best color. 2. Horology, a watch glass; the word for this use derived from the fact that the earliest transparent protection for watch dials was by means of discs of polished rock crystal. “Unbreakable” crystals are made of transparent plastic materials.
crystal lifter – A multi-pronged adjustable tool used to constrict the circumference of a plastic watch crystal and allow its removal from a bezel.
crystalline – A reference to the internal structure of a solid, by which it is understood that the molecules are in a definite arrangement in relation to each other. crystalline substances possess certain properties related to their internal structure; these properties remain unaltered regardless of whether or not there is an external shape, or crystal, which reflects the internal molecular arrangement.
crystalline emerald – Misleading term for a glass imitation (green glass bottom, white glass top) of a soldered emerald. See SOLDERED EMERALD.
cubic – A crystal system in which the shapes assumed are referred to three sets if axes of equal length and at right angles to each other. The cube, the octahedron and the dode-cadron are characteristic forms of this system, also known as the isometric system. Substances crystallizing in this system have no double refraction and none of the properties related to it like dichrosim. Diamond, garnet, lazurite and spinel are some of the gem minerals crystallized in this system.
Cuckoo clock – A clock, usually in a carved wood case, with the figure of a bird appears at an opened shutter at each stroke of the hour-striking. Most cuckoo clocks are made in the Black Forest (Schwarzwald) district of southern Germany. A quail is added to denote quarter hours.
cuff bracelet – Wide, solid bracelet similar to a cuff.
cuff link – A device consisting of a front ornament and a snap or swinging back, used to keep button-less cuffs closed.
culasse – (koo-lass’) The pavilion.
culet – (kew’let) The small facet at the bottom of a brilliant-cut stone. Also culette or collet.
cultivated pearl – Cultured pearl.
cultured pearl – A pearl resulting from the planting by man of a nucleus and/or a piece of mantle tissue from another mollusk in the body of a host mollusk, around which the latter deposits layer of nacre. Shapes include sphere, button, egg, oval, drop, pear, semi-baroque and baroque. Among colors are pink white; light, medium and dark cream; blue; gray; and black-sometimes with green, blue or rose overtones. Most cultured pearls have been subject to some color adjustment, generally a water-base protein or organic dye; this is a matter of slight concern unless the drill holes or strings are discolored. It is unfair trade practice to use the word pearl to describe a cultured pearl unless it is preceded by the word cultured or cultivated. See NACRE; NUCLEATED; NON-NUCLEATED; LUSTER.
cupellation – To assay or refine in a cupel-a shallow, porous cup used in refining precious metals.
curb – 1. Curb-pins: The regular pins, embracing hairspring. 2. Compensating curb: An early compensating device consisting of a bimetallic bar, carrying one of the regulator pins to in-crease and diminish space between pins to change time rate of hairspring and balance. See COMPENSATING BALANCE.
curb chain – Flattened link chain.
curves – (terminal) Refers to the profile forms of the overcoils, or inner terminals, of Breguet hairsprings; and to the upper and lower terminals of cylindrical hairsprings for chronometers.
cushion – Descriptive term used in connection with various forms of stone cutting to indicate a generally rectangular shape.
cut – 1. When used in relation to gem stones this word means a fashioned gem, as opposed to an uncut or rough gem. With most stones, cutting and polishing are two processes, the stone is first shaped and then it is polished. Diamonds are shaped and polished pretty much at the same time. See BRUTING; CLEAVING; BRILLIANT; BRILLONETTE; BRIOLETTE; BAGUETTE, etc. 2. Of files, numerals denoting the coarseness or distance 1, 2, 3, 4, 5, 6 being in order of coarse to finer cuts.
cut balance – A balance with its rim cut through, near each of its arm, to separate it into two segments. See COMPENSATING BALANCE.
cut-corner-triangle cut – A fancy diamond shape, a triangle from which two of the corners have been cut.
cuttlefish bone – Dried porous bone used for quickly making molds for casting small pieces of jewelry. The pattern is pressed between two pieces of bone after cutting out a partial recess in each half of the mold for the pattern; pressure completes the mold in details.
cutting grade – Diamond. A system for determining the quality of the cutting of a diamond, in terms of its departure from a standard. a. The Scan. D.N. scale (1970) deals solely with proportions and symmetry finish faults being considered under “clarity.” Graphical comparisons are made with the Scan. D.N. Standard Cut. Four grades are used: very good, good, medium, and poor, with the following sub-grades for stones weighing 0.50ct. and more: for very good, 0, 1, 2; for good, 3, 4, 5; for medium, 6, 7, 8; for poor, 9, 10. b. The American Gem Society System (1975) defines grade of cutting in terms of departure from ideal proportions and finish. It assigns a cutting grade, on a scale of 0 through 10, by combining a proportion grade of 0 through 10 with a finish grade of 0 through 4. The proportion grade for a round brilliant-cut diamond depends on the percentage of weight loss if the diamond were recut to the “ideal” proportions published by Marcel Tolkowsky in 1919, the formula being: (present weight minus “recut weight”) divided by present weight equal weight loss %. See AMERICAN CUT; TOLKOWSKY, MARCEL; EUROPEAN CUT; SCAN, D.N. STANDARD CUT; OLD-EUROPEAN CUT. c. Colored stones. In grading colored stones for cut, GIA teaches the following system: excellent, very good, good, fair, poor.
cyanide – (sign’ah-nide) A compound of cyanogens with another substance. The cyanides of potassium and of sodium are much used for dissolving tarnish in silverware. One once of cyanide dissolved in one quart of water in an average proportion; if the tarnish is thick and stubborn, the solution may be made stronger in cyanide. VERY POISONOUS!!!
cycle – A regularly-recurring period of time. In clocks and watches, the swings of the balance or pendulum or the vibrations of tuning fork or crystal oscillator. The swing from one side and back again of such an oscillator in one cycle or Hertz (Hz).
cycloid – (sigh’kloid) A curve traced by a point on a circle that rolls along a straight line used in designating profiles of gear teeth. See EPICYCLOID.
cyclops agate – An agate with a single eye. See ALEPPO STONE: OWL-EYE AGATE.
cyclotron treatment – The principal diamond coloration process of the 1940’s and early 1950’s. Stones, exposed culet-up to the deuteron beam, turned dark tourmaline green, red-brown, or yellow, the depth of penetration showing under magnification as an umbrella around the culet. In later years, exposure to fast neutrons eliminated the telltale umbrella, but it was discovered that the treatment and subsequent heating caused absorption lines not known in natural “canaries.” See PILE-TREATED STONES.
cylinder escapement – A form of escapement in which the balance staff is a steel hollow cylinder half cut away below the balance, the edges of the cylinder-shell being the pallets, receiving their impulse-lifts from wedge-shaped escape wheel teeth. During the motions of the balance, except during impulse and drop, the escape wheel teeth press against the outside of the cylinder, making this a frictional escapement, therefore inferior in timekeeping to the lever or chronometer escapement. A feature characteristic of cylinder escapement in the “chariot”- an adjustable base to which is screwed the balance pivot clock, and in which the lower balance pivot jewels are set. This chariot may be fastened at a variety of distances from the escape wheel, providing an adjustment for the depth of lock in the escapement. The cylinder escarpment was the earliest improvement, in watch escapements, over the verge escapement, and was invented in its present form by George Graham of London, England, about 1725. It is still used in large quantities of the cheapest watches made in Switzerland. See DETACHED; FRICTIONAL; HORIZONTAL.
cylindrical hairspring – A form of balance spring mostly used in marine chronometer, with its coils in helical instead of spiral form. This allows both terminals to be given full curves; the great height of the helical spring in allowable because there is no need to design chronometers to be “thin” as watches must be.
cyma – A double curve concave at the top and convex at the bottom.
cymophane – (si’mo-fane) Name given to chrysoberyl cat’s-eye.
cyprine – (sipp’rinn) A blue variety of vesuvianite.
cyst pearl – (sist) Complete pearls which form in the body of the oyster, as opposed to blister pearls which form on the shell.
Czochralski process – (cho-kral-skee) The method of high-melting substance synthesis by “pulling” a crystal rod (pulled boule) from a pot of pure, but molten, material. An alternative to the Verneuil furnace for congruently melting, instantly crystallizing substance like corundum and YAG. The method originated in 1918 by J. Czochralski.
dactylography – (dak-till’i-og”ra-fi) The lore and art of engraving gems.
daily rate – The day-to-day variation from precise time a watch or clock gains (+) and loses (-).
dammar – A resin from pinaceous trees of Australia, New Zealand and the East Indies which is sometimes used in imitations of amber. See KAURI GUM.
damped wave – The diminishing alternating current in a coil such as in a modern demagnetizer.
damping – The time it takes a balance to come to rest after it has been brought to the extreme of its arc and then allowed to oscillate freely without assistance from its escapement.
danburite – An uncommon mineral, a pale yellow to white calcium boron silicate; its properties resemble those to topaz. Gem material has come from Burma and colorless crystals have been found in Japan, Switzerland and a few other places. Named for Danbury, Conn., where it was first found. The name has been used in a misleading way for light red synthetic corundum.
dapping-die – An iron cube with a variety of concave sinks on its faces, used with corresponding punches to produce cup-shaped form in sheet metal.
daourite – Also spelled daurite, a name for red tourmaline. See RUBELLITE.
dark-field illumination – A feature of some magnifiers, combining side illumination with a black background; the stone and its characteristics can be observed with little confusion from reflections. Consequently, many black-appearing inclusions in diamonds may be seen, correctly, as without color.
dark yellow – A diamond color-grade, paler than canary.
dart – Horol. A pointed piece of metal on the fork of a lever escapement, which contacts the roller edge when the safety action functions.
date aperture – The opening in a dial to reveal the date.
date corrector – A push lever to advance the date disk until the correct date appears.
date disk – The disk in a calendar timepiece upon which the 31 days are numbered and shown in the dial aperture.
date, international line – See INTERNATIONAL DATE LINE.
datolite – (datt-o-lite) A colorless to pale green mineral, a hydrous calcium boron silicate, which is rare cut as a gem for collectors. An opaque variety found in Michigan is white, cream-colored, or pink, and has been cabochon-cut by many amateur lapidists.
day disk – The disk in a calendar timepiece upon which the days of the week are printed and shown through the dial aperutre.
d. c. – Jewelry. A trade abbreviation for “diamond (brilliant) cut.”
dead-beat escapement – An escapement in which the escape wheel remains stationary, not recoil between its forward motions. This is accomplished by making the profiles of pallet locking-faces to be arcs concentric with the axis of the pallet arbor.
dead-center lathe – A lathe in which work is held between two stationary centers and rotated on them by a pulley fastened to the work and driven by a stringed bow operated by hand. In horology this principle has survived mostly for lathes used for altering pivots in adjusting watches.
De Beers Consolidated Mines Limited – Conducts the mining of about 45% of world’s gem and industrial diamonds, the manufacture of synthetic diamond for use in industry and the marketing of the vast majority of all newly-mined rough gem and industrial diamonds through associated companies.
decalcomania – (dee-kall’koe-may”ni-a) Method of decorating clock cases, also other objects, including show windows, by transferring a printed design from wet paper; the design comes off the paper and adheres to the glass or wood. In dinnerware, even fine china, decal design are pressed in place and transferred when wet, after which the piece is glazed.
decantation – Grading abrasive powders by mixing with liquid, and pouring off at intervals, the finer grains remaining suspended the longer time in the liquid. Oil is used for decanting diamond powder; water for most other powders.
decarbonizes – To remove carbon; decarbonization is what happens when steel is overheated for hardening. See BURNT.
decimal timer – A stop watch whose dial is calibrated in decimal parts of a minute and seconds.
deck watch – A potable precision watch used on shipboard to compare local time with the ship’s chronometer, local time having been obtained by navigational instruments.
decorative stones – At the foot of the totem pole for genuine stones, below the categories precious and semi-precious of popular usage. Abundant and generally translucent or opaque, they can hardly aspire to higher ranking, although many are very decorative indeed. Agates, jasper and chalcedonies constitute the majority of them.
dedendum – The non-acting portion of the length of a gear tooth, from the bottom of the addendum to the base of the tooth. See ADDENDUM.
Deep cut – When a diamond is cut too deep, it will lose or leak light through the side or bottom. This results in less brilliance and value.
degreasing – The chemical, liquid or mechanical means of removing soil or coagulated lubricants from parts of a timepiece.
degree – 1. Unit of measure of temperature; see FEHRENHEIT. 2. A unit of angular measure equal to the center angle formed by 1/360th of the circumference of a circle.
delatinite – The lighter weight of one of two varieties of Rumanian amber, coming from Delatyn. See ALMASCHITE.
delawarite – Aventurine feldspar from Delaware County, Pa.
delta – Proposed name for a price key three times dealer cost. See KEYSTONE; TRIPLE KEY-STONE.
demagnetize – To remove effective magnetism from magnetized steel parts of a watch, by passing the watch through a hollow coil of wire in which a diminishing alternating current flows.
demantoid – (de-man’toid) A bright green variety of andradite garnet. Rare in larger sizes, though frequent in small stones and generally sold under the false and misleading name of “olivine,” it is among the most attractive of gems, with a high index of refraction, and stronger dispersion than a diamond. So far clear stones have come only from Russia. False and local names include: “Bobrowka garnet,” “Siberian chrysolite,” “Uralian olivine,” and “Uralian emerald.” Also see CHRYSOLITE; OLIVINE; TOPAZOLITE.
demantspar – Same as adamantine spar.
demidovite – Blue compact chrysocolla from Nishini-Tagilsk, Russia. Some pieces have been cut.
denatured alcohol – Alcohol with small proportion of chemicals added to render it unfit for drinking; used for cleaning watches, jewelry, etc.
dendritic agate – Agate with tree-like marking, caused by iron or manganese oxides.
dendritic opal – Common opal with markings like those of dendritic agate.
Denison escapement – The “double three-legged gravity” escapement for tower clocks, designed in 1854 by Sir E. B. Denison for the clock on Parliament buildings, London.
Dennison gauge – A slotted flat, brass gauge based on the millimeter used to gauge the within and thickness of mainsprings.
dental brush – Mandrel-mounted or unmounted brushes of bristle or wire for polishing in limited access areas.
depolorize – To demagnetize, thus to remove any traces of magnetic polarization.
Depth – 1 measurement of diamond from the top of the crown to the bottom of the pavilion. 2 The engagement between a pair of gears.
Depth Percentage – width ÷ depth = depth°
depthing tool – An adjustable holder for a wheel and pinion, for inspecting a depth, or transferring its center-distance to plates in watch or clock work.
Derbyshire spar – Fluorite.
desert amethyst – Misnomer; a western United States term for glass colored violet by long exposure to the rays of the sun. The cause of this change is supposed to be a manganese impurity in the glass which is affected by the light. Modern glass does not turn purple.
detached escapement – An escapement in which the escape wheel is held away from contact with balance by a third part, like the pallet in lever escapement or the detent in chronomenter escapement, except during impulses. See FRICTIONAL ESCAPEMENT.
detectoscope – Trade name for emerald filter.
detent – A part in mechanism on which some other parts rests during a phase of action, as the locking detent in a chronometer escapement, or the detent in setting work of some watches.
development – The action of a spiral spring, mainspring or hairspring as it unwinds.
dewaxer – A device for eliminating much of the invested wax before burnout by means of steam. Wax thus recovered may be reused.
dewpoint – The temperature, under certain, varying conditions, at which water-vapor condenses.
diabase – (die’ah-base) A dark compact igneous rock with lath-like feldspar crystals sometimes used as a decorative stone.
Diagem – Promotional name for strontium titanate.
diagnosis – The result of a systematic examination, as of an out-of-order watch. A good word to use when giving an estimate of cost of repairs.
diakon – Another term for a polymerized acrylic ester, or plastic.
dial – The plate fixed behind the hands of a timepiece, marked with divisions and numerals for indicating time by movement of the hands.
dial, arched – Usually Dutch 18th Century clock and watch dials had the minute track between numerals in an arch.
dial-countersink – A pointed piece of abrasive material for opening or chamfering holes in enamel dials.
dial, double sunk – A dial in which the chapter ring is one level above the central portion and the second “bit” is one level below the central portion.
dial-down – One of the positions in which watches are timed in being adjusted, with dial horizontal and facing downward.
dial, equation – A dial upon which are shown the variations of solar time with mean solar time (i.e. equation of time).
dial foot – One of the soft metal pins on back of the dial to fasten it to lower plate of movement.
dial-gauge – A sensitive measuring instrument in which the movement of its jaws is multiplied by levers or pulleys and indicated by a hand on a dial.
dial, hip screw – Screw which secures a watch dial leg by a shape hip-edge extending below the screwhead.
dial, lunar – The revolving disk showing the moon’s phases.
dial-plate – The main or lower plate of a watch movement to which the dial is attached.
dial, railroad – A dial on a large pocket watch with large, prominent numerals, more often in Arabic.
dial screw – The screw in the lower plate of a watch, to fasten the dial foot.
dial, skeleton – A dial with all unnecessary metal removed to reveal the movement behind it.
dial, tidal – Dials which use a “rise and fall” action behind the regular dial to indicate tidal schedules.
dial-train – Gearing, under the timepiece dial, which reduces the rate of turns usually from one per hour at center post, to one in 12 hours, to provide motion for an hour hand.
dial-up – One of the position in which watches are timed in being adjustable, with dial horizontal and facing upward.
dial washer – A pierced concave masher made of thin, springy sheet metal placed between the hour wheel and dial, to hold the wheel into the gearing with minute pinion. Used in repairing cheap watches.
diallage – (di’ah-lai) Chemically similar to diopside, but found in compact masses with schiller effect, and used as a dark brown, greenish or grayish decorative stone. See PYROXINE.
diamantine – (di’ah-man”tin) A chemically prepared crystallization of boron, used as an abrasive powder for polishing steel.
diametral pitch – In designing gearing, a measurement unit determine by dividing the pitch diameter of a wheel by the number of the teeth in the wheel.
diamond – From Old French diamante, which derives from the Latin adamas, “unyielding.” A mineral composed of pure carbon, the hardest of all known substance and a valued gem, found in many colors. It crystallized in the cubic system. It has a reflective index of 2.24 and strong dispersion. For varieties, see BORT: CARBONADO: BALLAS: CRYSTALS. Many diamond terms will be found through the glossary, too many to re-list here.
diamond broach – Thin tapered copper wire charged with diamond powder, for enlarging and polishing holes in watch jewels.
diamond burs – Abrasive wheels, burs and drills composed of embedded diamond grains, mounted on metal forms. Used for drilling and grinding hard substance.
Diamond Certificate – Award from Gemological Institute of America for completion of its correspondence or residence course on diamonds.
Diamond Corporation – Part of the Central Selling Organization, which functions as the contractual purchaser from diamond producers outside the De Beers group. See CENTRAL SELLING ORGANIZED; DE BEERS CONSOLIDATED MINES LIMITED, DIAMOND TRADING COMPANY.
Diamond Council of America – An organization founded by credit jeweler firms, offering courses in “diamontolgy” and gemology to employes of those firms and rewarding successful students with title “Certified Diamontologist” or “Guild Gemologist.”
diamond cut – Same as BRILLIANT CUT.
Diamond Grading Reports – There are many recognized gemological laboratories that can grade your diamond for a fee. The most well known is the GIA, Gemological Institute of America.
diamond grading systems – See CLARITY GRADE; COLOR GRADE; CUTTING GRADE.
diamond lab – An abrasive wheel or file, made of soft metal, usually copper, changed with pulverized diamond.
diamond paper – Strong tissues paper, often with white or pale blue lining, folded into a small envelope, often 3” to 3¾” x 1¾” to 3” in size, for polished diamonds or other stones. Stones should be carried in separate envelopes or wrapped in lint, to avoid damaging each other.
diamond polishing lathe – High-precision lathe using diamond tools to internally and externally cut and polish rings and watch cases.
diamond powder – Particles of natural or synthetic diamond, most of it less than 1/50,000 of an inch in size, used for industrial work and, mixed with olive oil, for cutting and faceting diamonds and harder colored stones.
Diamond Producers Association – Sells rough diamonds to the Central Selling Organization, sets policies and quotas, makes marketing agreements with other producers. It represents the Government of the Republic of South Africa, which owns diggings in Namaqualand; the Diamond Corporation; the De Beers Company and its associated producers. Premier and Consolidated Diamonds Mines.
Diamond Trading Company – Part of the Central Selling Organization which conducts the sales of rough gem-quality diamonds in London, after it has sorted and valued them into more than 2000 different classifications. See CENTRAL SLLING ORGANIZATION, DE BEERS CONSOLIDATED MINES LIMITED.
diamond tweezers – 1. Tweezers with rounded ends, corrugated tips and rather weak springs, to hold diamonds and other stones. 2. Instrument with three springs-controlled prongs issuing from tube-like body. With increased pressure on protrude further, thus enabling various sizes of round stones to be securely held.
DiamondLite – Trademark for a diamond-color grading instrument designed and marketed by the Gemological Institute of America. Stones are viewed on white acrylic plastic under pure simulated north daylight from phosphorescent-coated fluorescent bulbs, and comparison-grade for relative whiteness against a set of standard stones. In includes an ultraviolet tube to bring out fluorescence, if any is present. See COLOR GRADE.
Diamondscope – Trademark of American Gem Society for a binocular microscope to which an illuminated stage has been added, which permits the examination of gems in either direct of indirect light, coming from directly below the stone or from around the edge of the stage.
diaper – A type of ornamentation produced by repeating a geometrical pattern in small squares.
diaspore – (di’-a-spore). An aluminum oxide which rarely occurs in crystals large enough to cut white, grayish or violet gems for collectors. Very unusual and, to date, of no significance to the trade.
diasterism – Asterism phenomena observed by transmitted light. See ASTERISM; EPIASTERISM.
dichroism – (di’kro-ism) The property possessed by many crystallized substance of transmitting (or conversely, absorbing), different colors of light in different directions through the crystal. Pleochroism in the general term: dichroism means that two colors are transmitted in two distinct crystal directions at right angles to each other, and refers to crystals of the tetragonal and hexagonal system. Trichroism (three colors in three directions) refers to orthorhombic, monoclinic or triclinic crystal. See PLECHROISM and DICHROSCOPE.
dichroite – Iolite, this name refers to the strong plechroism of the mineral.
dichroscope – (die’kroe-skope) An instrument, consisting of a calcite rhomb, for the detection of dichroism in a gem. It separates the two vibrations directions of the light passing through a doubly refracting gem, and by placing them side by side, permits accurate color comparisons. A similar effect can be obtained from two sheets of polaroid in contact with the transmission directions at right angles. See BIREFRINGENCE.
die – 1. A block usually of steel with a hollowed-out form cut in it, into which soft metal is struck or pressed to produce piece of work in manufacturing. 2. The thread-cutting hole in a screw plate.
die casting – Process of making a casting by forcing molten metal into a metal mold or die under great pressure.
dielectric – A substance such as mica, glass or other non-conductor, separating electrical changes.
die sinking – Die sinking or die cutting is the art of cutting, usually by hand, the form and ornament of a given article into a block of tool steel. This forms the die from which spoons, forks, jewelry and kindred articles are stamped out.
die struck – Gold jewelry. An object that has been produced by striking gold sheet or tubing on one or between two dies. The stamping hammer forces the gold, under tremendous pressure, into every crevice of the die and forms sharp, high detail. Compressed, strengthened and hardened, the metal takes a high polish, is easier to solder, and weighs more then an identical piece made of cast gold because the molecules are squeezed tightly together.
differential – A device in a watch to indicate reserve power in the mainspring. First used in clocks to indicate the equation of time.
diffraction – An optical phenomenon of light; the production of colors fringes around a beam which has passed through a narrow slit or which has been reflected from a surface with recurrent irregularities, such as a ruled diffraction grating. Diffraction takes place from the thin overlapping scale on the surface of a pearl. See ORIENT.
diffraction jewelry – A jewelry object whose surface in composed of a series of concentric circles, too close to be seen with the unaided eye. The overall effect is a rainbow-like iridescence.
diffusion column – A piece of apparatus used for the determination of specific gravity. It consists of a tube containing a heavy liquid has been dripped. Through natural diffusion, a successively greater density with increasing depth is obtained. By noting the resting place of two particles of known gravity in this column, it is possible to make a fairly accurate deter-mination of the gravity of an unknown substance which floats somewhere between them.
dimethyl glyoxime – Chemical used, dissolved in water, for testing purity and for identification of metals in the platinum group. Also used to, reveal the presence of nickel in meteoric iron, in the testing of meteorites.
dimorphism – Crystallization of a chemical compound into two different crystal forms, such as calcium carbonate into rhombohedral calcite and orthorhombic aragonite, or carbon into isometric diamond crystal and rhombohedral graphite flakes.
diode – An electronic valve which allows current to travel in but one direction.
diopside – (di-op’side) A member of the pyroxene group of minerals, a calcium-magnesium silicate, ranging from white to deep green or almost black. Clear green gems have been cut from material found in New York, Madagascar, Tyrol, Brazil, Ceylon, etc. See ALALITE; CHROME DIOPSIDE; DIALLAGE; VIOLAN. Considerable quantities of diopside are present in some of the Mexican jadeite, together with albite and anorthite feldspar. See MAYAITE; TUXTLITE.
dioptase – (di-op’tase) An emerald green hydrous silicate of copper which sometimes crystallizes in fair-sized hexagonal prisms. It is too soft and brittle for any gem use except for collectors, but is beautiful in appearance and highly valued, as minerals go, for collections.
dip – A chemical solution for brightening or coloring quantities of cheap jewelry economically by immersion instead of by buffing.
direct current – Electric current that flows continually in one direction; used for electro-plating, and in battery-driven clocks. See ALTERNATING CURRENT.
direct seconds – A watch in which the center seconds hand is motivated directly from the centered fourth-wheel pinion.
Dirilyte – The trademark name of an alloy having the color of gold, composed of copper 88 per cent, aluminum 10 percent, nickel 2 per cent.
discharging pallet – The pallet in an escapement which last contacts an escape wheel tooth as the tooth passes through the escapement.
disengaging friction – In gearing, friction between teeth after their point of contrast has passed the line of centers. See CENTERS, LINE OF; ENGAGING FRICTION.
dispersion – The spreading of the rainbow colors of white light when refracted by a transparent substance with inclined sides, such as a prism or cut gemstone. The ray are separated be cause they are slowed and bent according to their wavelengths, the shortest ones, violet, being bent the most and the longest, red, the least. Violet rays transit diamond at 75,000 miles a second; red 77,000 miles a second. The dispersion of gemstones is measured by the difference of its refractive index for the two rays; it is the controlling factor in fire. Dispersion varies greatly among gemstones; is high, 0.044, in diamond. Both Titania and Fabulite have fabulous dispersion, giving rise to polychromatic wedges of light spread even more widely than those from diamond. But they lack diamond’s unrivalled hardness to keep them bright and polished, and under the same conditions cannot long rival the carbon gem. Dispersion cannot be seen when light passes through a medium with parallel sides because the emerging ray reunite. See REFRACTION; REFRATICE INDEX.
divalent silver oxide cell – A battery said to produce energy in a timepiece for a longer time than a standard cell; its silver combines with twice the normal number of hydrogen atoms, thus emitting more ions. Divalent silver is used for thinner and/or longer-lasting batteries.
diver’s watch – A water-resistant watch, some models of which may be immersed to depths of 660 feet, or more.
dividers – Tool for drawing circles, or spacing divisions of length, formed of two arms pivoted adjustably together at one of their ends, the other ends pointed for the uses started.
dividers, electronic – That part of an integrated circuit of a timepiece that divides the high frequency of the quartz resonator in steps to a frequency low enough to index the time dis-play.
dividing plate – A disk with numbered series of notches or holes to engage a latch, for spacing teeth in cutting gears wheels and pinions.
dixieme gauge – A Swiss gauge dividing millimeters into tenths.
doctor – In electroplating, a piece of sponge dipped in solution, wrapped around an anode and applied to a portion of a large article, to plate a spot without plating the entire article in a bath.
dodecahedron – (do’deck-a-hee’dron). Crystallography. One of the more common forms of the cubic system, having 12 lozenge-shaped or rhombic faces.
dog – A lathe clamp to connect the turned work to the driving force.
dog collar – A wide flexible band, usually set with precious stones, which fits snugly around the neck of the wearer, like a dog’s collar.
dog screw – A screw with a portion of the circular head cut away on one side for fastening watch movements in cases.
dog-tooth pearl – An elongated baroque pearl.
dome – 1. Horology. European term denoting an inside cap in a watch case. b. Part of balance cock on some American watches, holding jewel setting. 2. Jewelry. A convex decra-tion made by placing a metal disc in a hollow in the dapping punch to force the metal into the hollow.
dop – Instrument in which a diamond is held for polishing and bruting; a metal cup filled with low-melting-point lead alloy in which the rough diamond in embedded. It is now frequently a small adjustable vise which holds the diamond in most position (mechanical drop). The instrument in which the stone is cemented for bruting in also known as a dop, as are the wood or metal rods to which the colored stones are affixed for cutting.
doped – One of the standard synthetics like YAG, scheelite, corundum, etc. to which a small amount of some impurity has been added to affect its electronic behavior.
doré – (doe-ray’) 1. French for gilded or gold-plated. 2. A mixture of silver, gold and certain base metal impurities.
dot agate – A variety of agate with rounded colored spots in a white matrix. See ST. STAPHEN’S STONE; POLKA-DOT AGATE.
double cabochon – An un-facetted form of gem cutting. Both the top and bottom of the stone are given a rounded convex shape. See CABOCHON.
double-cut brilliant – A diamond cutting with two rows of facets on the upper side. See TRIPLE CUT; SINGLE CUT BRILLIANT.
double Dutch rose, double Holland rose – A rose-cut stone with 36 triangular crown facets and a large culet. See HOLLAND ROSE; ROSE. Also known as a “rose récoupee.”
double refraction – The division by crystals of transmitted light into two rays traveling at different rates on different paths and vibrating at right angles to each other. All translucent anisotropic crystals have the power to force vibrations into certain planes. See BIREFRINGENCE; ANISOTROPIC; ISOTROPIC; POLARISCOPE.
double-roller escapement – A lever escapement with separate impulse-roller and safety action roller.
double rose cut, double rosette – Two Holland rose cuts base to base, making a stone without a table or culet. See PENDELOQUE.
double-sunk dial – Dial with separate portions at different levels, inside the hour-and-minute circle and for the seconds circle.
doublet – 1. Any imitation or manufactured stone of two component parts. 2. In the trade, the doublet may be a glass imitation with a thin layer of genuine garnet fused on the top. The deep red color of the garnet only shows at the back. The sapphire doublet, for example, is blue glass with a natural garnet top. The harder exposed surface of the garnet protects the softer glass from rapid water. Also common today are doublets consisting of natural and synthetic corundum and of synthetic sapphire and strontium titanate. Other store combinations have been developed, particularly opals, imitations of emerald (“soudee emeralds”) and some of the diamond imitations.
dovetail – 1. In English lever escapement watches, a tapered bar of metal with hole and cap jewels for lower balance pivot. 2. In verge escapement watches, the metal wedge that holds the bearing for the inner escape pinion pivot.
dragonite – Fabulous stone said to come from the head of the flying dragon. Quartz pebbles were identified with these stones.
dravite – (dray’vite) Brown tourmaline.
draw or draft – A force that holds a fork in a lever escapement against a banking, to keep guard pin or point normally from contact with roller-edge. This force must be overcome to unlock the escapement, or whenever a severe jolt causes the safety-action to function.
draw bench – A bench with a geared handle at one end, used to draw wire too heavy to be drawn by hand.
draw-filing – Finishing a surface by rubbing it with a file held at a right-angle to the length of the work.
draw-in spindle – The part of a lathe-head that is turned by hand to draw in and tighten a chuck.
draw-plate – A steel plate with graduated holes, through which metals may be pulled or drawn to form wire. The holes in fine draw-plates are bushed with pierced diamonds with polished holes.
draw tongs – Heavy pliers used for drawing wire through drawplates to reduce the thickness. See TONGS.
drawing steel – Tempering; lessening the hardness of hardened steel gradually by slowly heating it. See TEMPERING.
dredger – A metal sifter or shaker used for serving powdered or granulated condiments. The early dredgers were used for sugar and usually had straight sides and mushroom domes, perforated in concentric circles. See CASTORS.
D.R.G.M. – Abbreviation, formerly stamped on watches or clocks or tools of German or Swiss manufacture, meaning Deutsches Reichs Gebrauchs Muster, a patent for six years only, a “petty patent,” registered in Germany without examination of its claims. See S.G.D.G.
drifting – Giving final form to a hole in a piece of work, by using a steel punch driven or pressed into the hole.
drill – A boring tool used for producing holes. The types of drills mostly used in horology are flat drills and twist drills. Pearl drills are countersinks for cutting recesses for setting flat-bottomed half pearls in jewelry.
drill chuck – An adjustable chuck for holding all sizes of drills.
drill hole – Since laser drilling has been introduced for the elimination of “carbon spots” in diamonds, a phenomenon which must be reported in diamond certificates. It consists of a slender, tube-like drill hole extending from the surface to a flaw. Easily visible, though extremely minute.
drill rod – Commercial name for tool steel rods in sizes from smallest up to about ¼-inch diameter, used by watchmakers for making staffs, stems, drills, taps, etc.
driven – In a pair of gears, one that is turned by another one. See DRIVER.
driver – In a pair of gears, the one that applies power to turn the others.
driving coil – The electromagnetic coil in a timepiece that impels the frequency unit.
driving-fit – In mechanical work, a fit between two parts that require force to put the parts together, as in the fit to the hole in a minute hand on the seat on top of a cannon pinion; or of roller on balance staff. See FRICTIONTIGHT; SLIP FIT.
drop – 1. Horology. In escapement action, the short motion of the escape wheel between its release from one pallet and its contact with the other pallet. 2. Jewelry. A small pendent piece, suspended from another part of a piece of jewelry, as on a bracelet or earring. 3. Silver-smithing. The slightly molded point of union between the handle and the back of the bowl in a spoon.
drop hammer – A guillotine type of press wherein a heavy steel block is dropped onto metal placed on a die, or between two dies. This shapes the metal to conform with the die.
drop lock – In an escapement, the amount or depth of locking of an escape wheel tooth by a pallet, at the instant when drop has occurred; this amount is measured in degrees of an angle with its vertex at pallet center, one of its side passing through point of contact of tooth and pallet, the other side passing through lower end of locking face pallet. See ESCAPEMENT; LEVER; CYLINDER; CHRONOMETER; LOCK.
drop pearls – Pearl-shaped or oval pearls.
dropping bottle – Bottle with glass extension to stopper for applying acids in testing precious metals.
dross – The layer of impurities accumulated at the top of a mass of melted metal in a crucible.
drum – The barrel, in a clock, on which the weight cord is wound, and unwinds as the weight pulls in driving the clock train; the first mobile of the train is the main wheel fastened to the drum.
drum escapement – A recoil escapement used in many French clocks of small size; now be-coming obsolete. See TIC-TAC.
drunken key – Key for winding a timepiece, in which there is a ratchet that prevents winding in wrong direction, used mostly for chronometers.
druse – A crystal-line surface, often the inner surface of a geode and the final silica layer of an agate nodule.
drusy – Coated with small crystal; containing crystal-lined carities.
dry diggings – Term used to differentiate diamond diggings in volcanic pipes from river or alluvial mining.
ductility – Property of metals enabling them to be formed when cold, by hammering, die stamping, drawing, rolling, etc.
ducut – Inexpensive diamond cut used infrequently during World War II, produced by grinding top of small crystal to form a table and polishing the other surface of the crystal. Also called duke cut, prince cut and prince’s cut.
dumb-vibration – In a chronometer or duplex escapement, the motion of the balance, at every other beat, when no impulse in given to the balance by the escape wheel. See COUP PERDÚ.
dumortierite – (du-mor’tee-yer-ite) A purple to blue aluminum borosilicate sometimes found in sufficient concentrations to be used for decorative purposes. It forms masses of fine inter-grown needle-like crystals.
dumortierite quartz – A blue variety of dumortierite found in California intergrown with quarts, sometimes sold as California lapis.
duo-in-uno – A form of balance spring used by some early chronometer makers, in which the upper terminal coil of a cylindrical spring is formed like a flat spiral spring.
duplex escapement – An escapement of frictional type, now mostly obsolete. The last large use of it was in watches made by the New England Watch Co., of Waterbury, Conn., between 1898 and 1912. Characteristics of it are the impulses slot in balance staff, and two sets of teeth in the escape wheel.
dust band – A thin metal band, placed between the edges of upper and lower plates of watch movements to keep dust out.
dust collector – A system comprising a hood, pipe, and reservoir, with suction, to draw residue from a jeweler’s polishing lathe, for protection to operator’s health, cleanliness of shop, and conservation of precious metal wastes.
dust pearls – Small pearls less than 1/25th of a grain.
dust pipe – In chronometers and some key-wind watches, a cup-like device mounted on wind-ing and setting arbor squares, its lip touching the inside of the key hole in the case cap, to exclude dust from the movement.
dusting – Surface enameling by dusting or sieving ground enamel onto adhesive coating on metal. See ENAMEL.
Dutch bort – Zircons from South African diamond mines.
Dutch metal, or Dutch gold – An alloy imitating gold, usually 80 percent copper and 20 percent zinc.
Dutch silver – Netherlands silverware, .800 fine. Imitations, intricately ornamented with human figures, windmills, dwellings, trees, etc., and made of electroplated copper or soft metal, were popular in the United States about 1912-1922.
Dutch striking – Some older Dutch striking clocks struck the coming hour at the half hour on a bell of one pitch, and the full hour on the hour on a bell of another pitch.
dwt – Abbreviation for pennyweight, unit for weighing gold. See TROY WEIGHT.
dyed jadeite – a. Green. Translucent whitish of yellowish cabochons are heated; plunged into cold water to induce fracturing; warmed in a solution using a blue and a yellow organic dye; dried, and placed in melted paraffin, which disguises cracks. Green-dyed jadeite is readily detectable. b. Lavender. More difficult to detect because various dyes are used.
dyeing – The artificial treatment of porous gem material such as chalcedony, turquoise, pearl and coral; in addition an artificial porosity can be induced in otherwise impermeable structures so that dye can be introduced. The most successful and permanent method pro-duces a chemical reaction inside the stone, precipitating the desired color. See BLACK ONYX; BLACK-TREATED OPAL; CHINESE RUBY; CULTURED PEARL; DYED JADEITE; TREATED TURQUOISE; SARDONYX.
dynamic (poise) – The condition of a watch balance-assembly, as to poise, while the watch is running; differentiated from static poise, which prevails when a balance is tested on the poising tool. See POISING; STATIC POISE.
dynamic light scattering – A type of liquid crystal display used in some solid-state timepieces; when selected numeral segments are agitated electrically, their molecules scatter, causing the liquid in front of them to reflect; the digits therefore appears as tiny mirrors.
dynamo – Machine for generating electric current; but particularly a generator of direct current, as for electroplating.
Dynatron – A Swiss electronic watch using transistors to impel the balance-motor.
dyne – A unit of force acting on a mass of one centimeter per second. The C.G.S. system.