Gablonz jewelry – Name for a variety of inexpensive glass imitation jewelry from the town of Gablonz, Czechoslovakia.
Gachala emeralds – Characteristically Chivor-like light-hued emeralds from a relatively new mine, in the Chivor area of Columbia.
gadolinium gallium garnet – Diamond substitute developed by Bell Laboratories and marketed as Diamonique II in 1975 by M. Landis Co. of New York, Inc. Weight more than twice that of diamond (a stone the size of a 1.20-carat diamond is 2.75 carats); r.i., 2.03; dispersion, .038; hardness, near 6.5.
gahnite – (gah’nite) Zinc spinel, dark green to black, in which zinc has taken the place of magnesium. See GAHNO-SPINEL; SPINEL.
gahnospinel – A name which has been proposed for the intermediate zinc-bearing magnesium spinel; blue, blue-green or lavender in color, and slightly higher in refractive index and density than normal spinel.
gaining rate – In adjusting or regulating timepieces; applied to timepieces that run faster than the standard rate of time; opposite of a losing rate.
galalith – An artificial product made from milk and formaldehyde, which is used to make horn-like products in imitation of tortoise shell, ivory, amber, and jet.
gallery – Metals in strip form, for making settings for stones in jewelry.
gallows tools – A cradle-shaped tool with “V” notches to seat pinion arbors while its leaves are filed, shaped or polished.
galvanometer – An instrument for detecting electrical current, its direction and intensity.
Gambia shell – A variety of pearl oyster shell with a green nacre and nearly eight inches in diameter at a maximum. Depending upon the exportation point it is known as Tahiti, Auckland or Gambia shell; the same animal is scattered around the islands of the southern Pacific.
gamboge – (gamm-boje) A natural gum, soluble in water, used for a “resist” to paint over portions of a piece of jewelry where a parti-colored design requires that no electroplating be deposited.
gangue – (gang) The non-ore minerals associated with an ore deposit. Fluorite and apatite are frequent gangue minerals of ore veins.
garden – Euphemistic description of the flaws in an emerald.
garnet – A large mineralogical group of silicates of complex composition, such as calcium-aluminum garnet (grossular), iron-aluminum garnet (almandine) and so on. They occur in igneous and metamorphic rocks, are among the commonest of gems, and are found in many colors. They crystallize in the cubic system and are commonly found in crystals. Common trade usage of the term refers to the red almandine and pyrope. See also GROSSULAR; PYROPE; ALMANDINE; SPESSAR-TINE; ANDRADITE; UVAROVITE; DE-MANTOID; YAG.
gas bubbles – The rounded bubbles seen in glass and synthetic stones which are taken as indicative of the origin of the stone. Natural stones often contain angular cavities.
gasket – The plastic or rubber ring in a water-resistant case to aid in its impermeability.
gate – Opening in a mold to permit entry of molten material.
gathering pallet – A single tooth on extension of a train arbor pivot in clock striking-work, that moves successive teeth on the count-rack which determines the number of strokes sounded at each hour. Also called TUMBLER.
gauge – A measuring device for determining diameters, thickness, height, etc. See BOLEY; CALIPER; DOUZIEME; GROSSMAN; LEVERIDGE; MICROMETER; SLIDE; VERNIER.
gauntlet bracelet – Wide, tapered bracelet, worn above the wrist.
gauss- The unit of magnetic intensity of a magnetic pole at a distance of one centimeter.
gearing – A device for transmitting motion, consisting of interacting toothed wheels. See TRAIN.
gedanite – (jed’an-ite) A fossil resin related to amber, but softer and lower in gravity. It contains no succinic acid which is a requirement for true amber. The name is from Gedanum, Latin name for Gdansk, Poland.
gem – A stone cut and polished for use in jewelry, which fulfills the requirements of beauty, durability and rarity. The word is frequently used in the trade to signify a fine stone of unusual quality. Sometimes used as a prefix to indicate rough from which a good stone could be cut, as “gem crystal.” Federal Trade Commission trade practice rules forbid use of “gem” for a stone or pearl which does not possess the beauty, symmetry, rarity and value to so qualify. Imitation stones and pearls may not be described as “gems.”
gem color – The perfection color of any specimens. See GEM.
gem gravels – The gem mineral-containing gravels resulting from erosion and soil removal of streams. Found in stream beds or former stream beds, as in Ceylon, Montana, etc. As a rule only a small percentage of the gravel pebbles are those of gem minerals; quartz and rock pebbles usually predominate.
gem materials – Natural substances favored for personal adornment because of their color, luster and durability. Amber and jet are vegetable products; pearls, coral and ivory of animal origin; the rest are mineral. See GEMSTONES.
Gemolite – Trademark of the Gemological Institute of America for its diamond and gemstone illuminator-magnifier. It combines wide-field binocular magnification with dark-field or
Gemological Institute of America – A non-profit educational institution dedicated to the advancement of the intellectual side of the jewelry trade. Gem-testing laboratories, residential and correspondence-course teaching are included in its services, together with gemological research and instrument development. Its headquarters is in Santa Monica; its eastern headquarters and New York Gem Trade Laboratory in New York.
gemologist – One who completes recognized courses of study of gem materials and/or passes examinations that demonstrate his competence to identify and evaluate gem materials. See GIA GEMOLOGIST DIPLOMA; CERTIFIED GEMOLOGIST; GRADUATE GEMOLOGIST DIPLOMA; GRADUATE RESIDENCE DIPLOMA.
gemology – The scientific, historical and legendary study of gem materials, as distinct from all the minerals scientifically studied in mineralogy. Frank B. Wade, an Indianapolis high school chemistry teacher whose articles had been published in Jewelers’ Circular, may have been the first American to use the term. In 1916, in the preface to his Text Book of Precious Stones for Jewelers and the Gem-Loving Public, Wade wrote: “it is hoped. . . that the method of presentation used in this book will make easy the acquisition of a knowledge of gemology.”
Gemprint – Trade name for a method of individualizing diamonds and other transparent faceted gems by photographing their reflections; developed by Ephraim Frei, Shmuel Shtrickman and Charles Bar-Isaac of Israel’s Weitzmann Institute, and marketed by William Levine of Chicago.
gemstone – A naturally occurring mineral found in the rocks of the earth, the chemical composition and internal atomic structure of which make it suitable for jewelry use: color, clarity, hardness, rarity and availability. While only a handful of minerals-perhaps 20 out of 2500—have such properties, there are many gemstone names, because a single gem mineral may have several gemstone varieties (e.g., the beryl family; emerald, aquamarine, golden beryl, morganite, etc., are phases of a single colorless mineral, beryllium aluminum silicate). The practice of separating gemstones into two arbitrary groups-precious stones and semi-precious stones—has lost favor in recent years; instead, all are termed gemstones.
generating circle – A circle rolling on another, describing an epicycloidal arc, used to arrive at watch tooth shapes. See EPICYCLOIDAL.
Geneva movement – Design of watch in which upper pivot bearings are all in bridges or cocks, so as to expose the entire train to view; also called bar movement or bridge movement design.
Geneva ruby – Misnomer for some laboratory-processed rubies sold in 1882 and 1883 whose origin is still uncertain, but which may have been made by melting small ruby fragments. Or they may have been of Verneuil type made before that method was announced. They disappeared from the market again as suddenly as they appeared.
geode – A partially hollow, rounded nodule of stone, often crystal-lined. Agate and amethyst in particular frequently occur this way. As a rule, the nodules are harder than the enclosing rock in which they formed, perhaps filling in gas bubbles in a frozen lava flow, and after their host weathers, they may be found as rounded hollow boulders. The reference to the earth (geo) in their name refers to their rounded outline. See DRUSE; COCOANUT.
German jasper – Common irregularly-shaped jasper masses, as opposed to ball jasper, etc.
German lapis – Misnomer for reddish jasper from Nunkirchen which is stained blue to resemble genuine lapis lazuli. Probably identical with the so-called Swiss lapis.
German moccass – Imitation moss agates, in which the pattern has been very skillfully placed on the stone. Their perfection makes one suspicious, otherwise one would be likely to accept them as genuine since they look so natural.
germanium – A whitish metal resembling tin used in semi-conductors.
GIA Diamond Certificate – Award from the Gemological Institute of America for completion of its correspondence or residence course in diamond buying, selling, grading and appraising.
GIA Gemologist Diploma – Award from Gemological Institute of America for completion of its correspondence or residence courses on diamonds, colored stones and gem identification.
Gibraltar stone – A banded light-colored onyx marble from a cavern at Gibraltar. See MEXICAN ONYX.
gilders’ wax – A paste, used to produce a rich color upon mercury-gilt work, made from oil and yellow wax, each 25 parts; acetate of copper, 13 parts, red ocher, 37 parts. The oil and wax are blended by melting, to which the other substances, pulverized, are added gradually.—Arnold Philip.
gilding – Coating any surface with a film of gold. On non-metallic surfaces gilding is done by coating them with an adhesive on which gold-leaf is laid. On metallic surfaces, gilding is done by electroplating, or by fire-gilding. See ELECTROPLATING; FIRE GILDING; GOLD FILLED; GOLD LEAF; VERMEIL.
gilding metal – A brass containing less than the ordinary proportion of zinc, used as base metal for manufacturing gold-plated jewelry and other wares.
gilt – Silver or base metal having gold deposited thereon by chemical or electro-deposition process; now usually applied to inexpensive articles on which the gold deposit is extremely thin. See GOLD FLASHED.
gimbals – A pair of rings pivoted diametrically to each other and to outer and inner cases of a marine chronometer, to keep the chronometer movement always level regardless of the ship’s motion.
gimmal rings – A class of rings dating from the first part of the 15th Century or earlier in which two rings are joined by a pivot and united to constitute a single ring, or may be separated and worn individually. Each circlet has a hand so placed that when both are brought together the clasped hands unite the two rings. Usually the ring was separated at the betrothal ceremony and the two parts worn by the betrothed persons; after the marriage both were worn by the wife. Also spelled gemmel or gemmow.
giogetto – (j’o’gett’toe) A black coral from the Mediterranean. See ACCARBAAR.
girasol – (jeer’a-sole) A word with the same significance as heliotrope, “sun turning.” It has been used for fire opal, in reference to the red or orange ground color of this material. It is also applied to a transparent opal with a colorless ground mass and a bluish internal opalescence. It is likewise a name which has been used for moonstone.
girasol sapphire – A name given to a sapphire cat’s eye, a luminescent sapphire in which there is no pronounced star.
girdle – 1. The outermost edge of a cut gem, the dividing line between crown and pavilion facets, the rim by which the stone is held in a setting. 2. Diamond. The ideal diamond girdle leaves only enough thickness to provide safety from chipping and a good setting edge thicker than “knife edge.” Its thinnest point might be about 1% of girdle diameter; its thickest from 1.5% to 2% for diamonds over % carat and 2% to 2.5% for smaller stones.
girdle facets – 1. The 32 triangular facets bordering the girdle of a round brilliant cut diamond, 16 above, 16 below. Also called break, cross, half, skew, skill facets. See UPPER GIRDLE FACETS; LOWER GIRDLE FACETS. 2. If the girdle itself is faceted, the stone is said to have a faceted girdle.
girdling – The process by which round diamonds are given their circular or fancy shape, also known as cutting, bruting or rounding. The diamond to be girdled is cemented to the chuck of a lathe with resin and shellac. While it spins, a second diamond held in the dop of a 2-ft. wooden tool is pressed against it. Fragments from both stones are caught below the lathe chuck and used as diamond dust. To girdle a fancy shaped stone, the lathe chuck can be made to run in an eccentric pattern. Before invention of power-driven machinery in 1891, girdling was done by hand; “one diamond rubbed against another until by mutual abrasion both take a form”-Benvenuto Cellini (1568).
gladstone – A covered serving dish made of metal usually silver or silverplate. The cover is dome-shaped and mounted on a pivot at each end so that it rolls back to uncover the contents of the dish.
glass gauge – A device for measuring diameters and heights of watch glasses or crystals.
glassies – A diamond sorting grade; crystals or glassies are perfect octahedrons of the best color.
glass, watch – A piece of any transparent substance over the dial of a watch to protect dial and hands. Made of glass, or plastic substance, to be “unbreakable;” also called watch crystal regardless of material used in it.
glaze – Glassy mixture of mineral substance with which a ceramic body is coated. In earthenware, it forms a protective covering. In china, it blends with the body of the ware into one vitreous whole.
glazier’s diamond – Bort or small crystals and corners for glass cutting.
gletz – Small cleavage cracks in a diamond.
glossing – Abrasive for producing high polish on steel parts of timepieces; oxide of iron, pulverized and graded by decantation. See DECANTATION.
glucydor – An alloy of copper and beryllium used in solid balances and in hairsprings.
gneiss (nice) – A metamorphic rock, essentially granitic in composition, but having a banded structure; a decorative building stone and the matrix of some gems.
goethite – (ger’tite) Anhydrous iron oxide often crystallizing in thin needles, which are then included in rock crystal making a sagentic quartz; a common quartz inclusion, especially in amethyst, mistakenly identified in Germany as cacoxenite, under which name it has been sold in the trade.
going barrel – Mainspring barrel in a watch, with gear teeth on its circumference; the barrel turns on barrel arbor pivots, which are stationary except during winding of spring. See FUZEE, MOTOR BARREL.
going train – In striking clocks, the gear-train that is part of the timekeeping side of the movement, as distinct from the striking train.
golconda – (goll-kon-dah) A term which is sometimes applied to old Indian diamonds of fine quality. It is derived from the name of a city in the State of Hyderabad, India, which was once a center of the diamond trade.
gold – A yellow-colored metallic element used for coins and jewelry since prehistoric times. Most malleable and ductile of metals, gold may be beaten into sheets as thin as .000003 inch and an ounce of gold may be drawn out into 50 miles of wire. Unalterable by heat, air or most corrosive agents, it forms one of a group of noble metals; the metal is, however, dissolved by aqua regia, a mixture of strong nitric and hydrochloric acids. Pure gold melts at 1063° C., and boils at about 2600° C.; its specific gravity is 19.3 and the chemical symbol is Au. Pure or fine gold is too soft for ordinary use, and it is hardened by alloying with copper, silver and other metals; alloys differ in their hardness, color (red, yellow, green, white in many shades), ductility, malleability, corrosion resistance and smoothness. See KARAT.
gold-backed – Jewelry made of laminated stock comprising an under layer of gold, with a layer of platinum exposed to view, for platinum appearance at less cost than solid platinum stock.
gold beating – The ancient art of producing gold leaf. For sign-painting, lettering, etc., an alloy of 23 karat gold is cast into small oblong ingots and reduced by a rolling mill to a ribbon 1/800 inch thick. Lengths one inch square are separated by ox membranes (goldbeaters’ skins), placed in a mold and beaten with a 16-pound hammer; successive cuttings and beatings produce an extreme thinness. For certain embossing an 18 karat alloy is used; for stamping hat-bands, 14 karat.
gold chloride – A combination of chlorine and gold, produced by action of hydrochloric acid on gold; the resulting salt is largely used in making solutions for gold electroplating.
gold electroplate – 1. A coating by an electrolytic process with gold, or with a gold alloy of not less than 10 karat fineness, to a minimum thickness throughout equivalent to 7-millionths of an inch of fine gold. (This means that where the fineness is less than 24 karat the thickness must be proportionately greater, so that the same amount of fine gold had been used.) If the coating is thinner than 7-millionths of an inch, it may be marked “Gold Flashed” or “Gold Washed.” If the coating is equivalent to 100-millionths of an inch of fine gold, it may be marked “Heavy Gold Electroplate.” 2. Watchcases. Watchcases electroplated with gold or gold alloy to a minimum thickness of 3/4/1000ths of an inch are marked “Gold Electroplate” or “Gold Electroplated,” optionally preceded by designation of the karat fineness of the gold alloy. Example: “18 Karat Gold Electroplate.” A thickness of I^/IOOO of an inch or greater may be described as “Heavy Gold Electroplate,” optionally preceded by designation of karat fineness of the gold alloy. See ELECTROPLATING.
golden beryl – Yellow to yellow-brown beryl.
gold filled – A plating by soldering, brazing, welding or other mechanical means of gold alloy of not less than 10 karat fineness, when the plating constitutes at least l/20th of the weight of the metal in the entire article. Synonyms: “Gold Plate,” “Gold Plated,” “Gold Overlay,” “Rolled Gold Plate.” The term must be preceded by the karat fineness of the plating, such as “14 Kt. Gold Filled,” “14 Kt. G.F.,” “14 Kt. Gold Plate,” “14 Kt. G.P.” or “14 Kt. Gold Overlay.” When such plating weighs less than l/20th of the metal in the entire article, the term “Gold Plate,” “Gold Plated,” “Rolled Gold Plate,” or “Gold Overlay” is preceded by a fraction showing the relative weight of the plating to all the metal in the article. Example: “l/40th 12 Kt. Rolled Gold Plate” or “1/40 12 Kt. R.G.P.” 2. Watchcases. With watchcases, “Gold Filled” designates a similar plating of not less than 3/1000″ in thickness. Example: “12 Karat Gold Filled” or “12 K G.F.” “Gold Plate” or “Roiled Gold Plate” designates such watch-case plating not less than 1.5/1000″ in thickness. Example: “10 Karat Gold Plate” or “10 K. R.G.P.”
gold flashed – Designation for a gold electroplate thinner than 7-millionths of an inch of fine gold. Synonym: gold washed.
gold leaf – See GOLD BEATING.
gold nugget – A water-worn mass of vein gold found in a stream bed or former stream bed. More or less rounded depending upon the amount of wear and distance of transportation.
gold opal – An alternative name for FIRE OPAL, possibly somewhat lighter and more yellowish in tone.
gold overlay – See GOLD FILLED.
gold quartz – Usually a milky-looking quartz containing streaks and masses of gold. Often polished and used as a gem, especially in gold-producing regions.
gold scales – A pair of balance-scales, well made but usually not of precision type, for use with Troy weights, in the jewelry trade. Modern gold scales are electrically controlled, extremely accurate and readings noted on an electrically illuminated dial in ounces, pennyweights and grains or ounces and thousandths of pennyweights, Troy.
goldsmith – A worker in gold; a jeweler.
gold smudge – See BLACK DERMOGRAPHISM.
gold solder – An alloy usually composed of gold, silver, copper and zinc and sometimes cadmium—and sometimes nickel in white solders-used for hard-soldering gold work. It has been the custom in the U.S. jewelry industry to use solders of lower karat fineness than the article to be soldered, and the stamping laws allow an extra margin in the fineness of the whole article, to provide for this. The practice has been rationalized by the belief that a lower karat solder is necessary in order for the solder to have a melting point safely below that of the article to be soldered. There are many who doubt the necessity for this. Solders with adequately low melting points can be produced for every commercial karat level, at the same karat. The lower karat solders have been eliminated in some European countries and in the mid-70’s were under attack in the U.S.
gold-spring – In chronometer escapement, a flexible strip of gold, fastened at one end to detent-body, its free end protruding slightly beyond end of detent, to be pressed against by unlocking jewel for unlocking the escapement, the gold-spring giving way at alternate beats to allow a “dumb vibration,” when escapement is not unlocked and no impulse is given. See PASSING SPRING.
goldstone – See AVENTURINE.
gold topaz – Erroneous name for light yellow-brown quartz. See TOPAZ and SPANISH CITRINE.
gold washed – Designation for a gold electroplate thinner than 7-millionths of an inch of fine gold. Synonym: gold flashed.
goniometer – (gon’nee-om”meet-er) An instrument for measuring the angles between the plane faces of a solid, usually crystals. Gemologically it can be used for measuring the angles of facets and for determining the refractive index of transparent solids, and of immersion liquids.
goodletite – Australian-New Zealand term for a green pyroxene or amphibole matrix with ruby corundum through it. Similar, on a smaller scale, to the Tanzanian green zoisite matrix with the large rubies at Longido. Goodletite-like rock has been found in North Carolina.
gooseberry stone – Grossular, in reference to a common yellow-green color of this garnet species, whose name is derived from the Latin name for the gooseberry family.
gorgulho – Brazilian term for diamond-bearing quartz gravel river deposits.
goshenite – (go’shen-ite)A colorless beryl, originally named for Goshen, Mass., where some was found.
gota de aceite – “Oil drops,” the first quality of emerald.
goutte d’eau – (goot doe) Colorless topaz, “drop of water.”
goutte de sang – (goot-duh-song) Red spinel, “drop of blood.”
gouverneurite – (goo-vair-noor’ite). Brown magnesia tourmaline from Gouverneur, N.Y. See DRAVITE.
grading systems (diamond) – See CLARITY GRADE; COLOR GRADE; CUTTING GRADE.
Graduate Gemologist Diploma – Award from Gemological Institute of America to holders of the GIA Gemologist Diploma for completion of its two one-week resident classes in diamond appraisal and gem identification, offered in Los Angeles and other cities across the country.
Graduate Gemologist Residence Diploma – Award from Gemological Institute of America for completion of its 26-week resident training program in Los Angeles or New York, offering laboratory work in both diamonds and colored stones.
graffito – Enameled surface into which a design has been scratched before firing. See ENAMEL.
Graham escapement – Clock escapement invented by George Graham, of London, Eng., about 1715; principal characteristic is pallets with locking faces concentric with pallet center, making of it a dead-beat escapement. See DEAD-BEAT ESCAPEMENT.
grain – 1. The earliest unit of weight, originally a grain of wheat or barleycorn, and the smallest unit in the Troy, apothecaries and avoirdupois systems. In the Troy system, long used for precious metals, 24 grains (gn.) = 1 pennyweight (dwt); 480 gn. or 20 dwt. = 1 ounce Troy; 5760 gn. or 240 dwt. or 12 ounces Troy = 1 pound Troy (1 Ib t). 1 grain = 64.798 milligrams; 15.432 gn. = 1 gram. 2. Unit of weight for pearls, equal to one-fourth carat; therefore, four pearl grains = one carat. 3. Term commonly used in diamond polishing to refer to cleavage directions. 4. In speaking of opal, it refers to the pattern of color flashes, for example: harlequin, bands, triangles, squares, etc.
grain marks – Also known as grain lines, knot lines or twinning lines, they represent a difference in grain direction across a twin plane; they may appear on the surface or within a fashioned diamond.
grain tin – The purest variety of block tin, advisable for use in making laps for polishing steel watch parts with rouge or diamantine.
grainer – A loose term for diamond weights in quarter-carat multiples; e.g., a stone that weighs about one quarter carat is sometimes referred to as a grainer; or one that weighs about three-quarters of a carat as a three-grainer.
gram – Unit of weight in the metric system, based on the weight of one cubic centimeter of water. It is equal to 15.432 Troy grains. One kilogram, 1000 grams, equals 2.2046 pounds.
grande sonnerie – (grahnd’shon’uh’ree’) Grand or full strike in clocks that strike quarter-hours. First the hour is struck on a single bell or gong, followed by a ting-tang on two gongs or bells for each quarter. Thus at 8:45, eight single strokes are sounded, followed by three ting-tangs (double strokes). Some strike the hours and four quarters on the hour.
grandite – A coined combination of grossular and andradite suggested for garnets of composition intermediate between the two.
granite – A fairly coarsely crystalline rock composed essentially of potash feldspar and quartz, usually with a few accessory dark minerals like mica, etc., usually formed by slow cooling, at depth, of a molten magma. See PEGMATITE.
granulating – Forming melted metals into grains for alloying, by pouring the metal slowly into a large vessel of water.
granulation – An ancient jewelry art by which small gold particles adhere to the surface without evidence of solder. Grains or minute spheres of gold used in granulation are formed by placing small pallions of gold between layers of powered charcoal in a covered crucible or iron box and heated in a furnace until melted. This produces perfectly formed spheres of unoxydized gold.
graphic granite – An intergrowth of large crystals of quartz and feldspar found in pegmatites, in which the quartz crystals are so arranged that their cross-sections resemble cuneiform writing. Also known as HEBREW STONE. See PEGMATITE.
graphite – Natural crystalline carbon, used for making crucibles for melting metals in jewelry work and to a limited extent as a component of lubricants for clocks. Black specks in diamonds are often called graphite.
grasshopper escapement – Invented by John Harrison (1693-1766), the action of levers and counterweights was ingeniously arranged so that no oil was required. Its action was similar to the slow-motion movement of a grasshopper’s legs.
graver – A cutting tool used by hand, for engraving, or for turning work in a lathe. See BURIN.
graver sharpener – Tool for guiding gravers being sharpened on oilstone to produce dead-flat faces; essentially an adjustable graver holder mounted on a roller which rolls on the oilstone and guides the work.
gravity escapement – Clock escapement in which impulse is given pendulum directly by a weight, which is lifted previously by power from the train; principally used in tower clocks; invented by E. B. Denison, 1851, for the “Big Ben” clock on Parliament buildings, London.
gray finish – 1. Horology. A type of finish for metal parts of timepieces, of a frosted or matted appearance, produced by rubbing a part on abrasive grains on a lap, so that the grains roll between the work and the lap and indent the work with a multitude of microscopic pits. From this we have also a term, “in the gray,” referring to a watch or a group of its parts that are fitted to each other in working order, but not yet given their final finish. 2. Silver. See BUTLER FINISH.
grease table – Device for catching diamonds used on the sorting tables and invented (1897) by George Labram and F.B. Kirsten. Diamonds alone of all the minerals contained in the blue ground adhere to the grease, while all others flow away with the water as tailings over the end of the percussion table. This gem-separator proved unsuccessful with rubies at the Burma Ruby Mines (1898).
grease wheel – A felt wheel buff, charged with abrasive mixed with heavy grease, for use on jewelers’ lathes for preparing metal surfaces for polishing.
great wheel – In a watch or clock, the toothed wheel that gears with the center pinion; the “first wheel” in a timepiece train, as: the toothed part of a going or motor barrel, fuzee, clockweight drum, etc. See TRAIN.
Greek key pattern – A pattern or border composed of lines or narrow fillets at right angles to each other, commonly known as Greek fret pattern.
green chalcedony – An imitation of chrysoprase made by artifically staining chalcedony.
green ear – Name given to a river pearl.
green garnet – Demantoid, uvarovite, or grossular. Erroneously applied to green enstatite from South Africa.
green gold – Gold alloy containing a relatively high proportion of silver. Eighteen karat green gold consists of 75 per cent fine gold and 25 per cent fine silver; green gold alloys of lesser gold content contain relatively small amounts of zinc and copper, besides silver.
green jasper – Jasper commonly used in Chinese carvings but coming from Siberia and colored by chlorite of iron.
green John – Green fluorite. See BLUE JOHN.
green quartz – Erroneous trade name for the green fluorite of which many decorative Chinese carved objects are made. See AVENTURINE.
green onyx – Trade name for green-dyed chalcedony.
greenovite – Sphene, colored rose by manganese, and rarely, if ever, seen in gem quality.
green starstone – CHLORASTROLITE.
greenstone – Nephrite, but has been used for chlorastrolite.
grenalite – STAUROLITE.
grey gold – A pale-colored alloy of gold and iron; or gold, iron and silver.
grinding – The rough shaping of a gem, in preparation for the polishing.
grinding lap – A piece of metal or other substance, shaped to reproduce its form on pieces of work, by action of an abrasive spread on the lap. To grind square or conical pivots, laps are shaped like files and used by hand; or are cylindrical, etc., for use on rotary pivot polishers; or are of large flat area for flattening surfaces of work rubbed on lap by hand. Laps for grinding watch jewels are made of copper charged with diamond powder.
grindstone – Abrasive wheel of natural stone, used with water for rough-shaping steel cutting-tools preparatory to sharpening on oilstone.
grommet – A metal ring surrounding a hole.
groove – The seat turned in top of mainspring barrel wall, into which barrel cover is snapped to fit; also the seat turned in watchcase bezel for crystal.
Grossman gauge – A caliper gauge for measuring, in millimeters, tenths and hundredths, diameters of the smaller parts of watches, such as pivots.
grossular – (gross’u-lar) A calcium aluminum garnet, usually light in color and including the gem hessonite. Grossular had been restricted to colorless, pale green and brown to rose red until the Nineteen Seventies when transparent green, with some advantages over emerald, was found in Tanzania and Kenya. Elsewhere, most of the gem pebbles come from Ceylon, where the brown crystals resemble and are confused with zircon. Few other localities produce stones which can be cut. A light green massive variety, somewhat resembling jade, has been found near Pretoria, South Africa, and has been sold under the name Transvaal jade, falsonephrite, African jade, garnet jade, etc. See GOOSEBERRY STONE, TSAVORITE.
guanin – (gwa’neen) The substance extracted from fish scales which is responsible for the iridescence of imitation pearls made of the essence d’orient.
guard chain – Originally, a long silver or gold chain from which keys, watch, or other object hung. In modern times a small chain attached to one end of a neck chain or bracelet; the other end of the chain is connected to a spring ring which engages a link on the opposite end of the bracelet or necklace. This is to prevent the loss of the jewelry should the snap or clasp open. See SAFETY CHAIN.
guard pin – In single-roller lever escapement, the pin set perpendicularly to the lever, that provides safety-action in connection with the edge of the roller table. See LEVER ESCAPEMENT.
guard point – In double-roller lever escapement, the metal finger set on the fork parallel to its top, projecting toward rollers, and that provides safety-action in connection with edge of safety-roller. See LEVER ESCAPEMENT; FORK.
guard-ring – A thin ring, inconspicuous in appearance, to wear on finger in front of a valuable ring, to prevent the latter slipping off. Guard rings are often worn in pairs, with or without stones, on each side of a wedding ring.
guard shake – In lever escapement, the freedom or play between guard-pin or guard-point, and the edge of the roller table. The amount of guard shake is measured as the angle of fork motion allowed between resting of fork-lever on a banking, and contact of guard pin or point against the roller edge.
guarnaccino – Vermeille garnet.
gudgeon – The shaft of a clock or lathe upon which a wheel or pulley turns.
Guides for Watch Industry – Adopted by the U.S. Federal Trade Commission May 14, 1968; amended Aug. 18, 1970.
guilloche – (gee-losh’) Decoration engraved on watch cases or jewelry by machinery; engine-turning; geometrical designs engraved as a base for decoration with translucent colored enamel, through which engraving can be seen.
gum anime – (gum-ah-neem’) A recent fossil resin, often containing insects. See COPAL.
gum tragacanth – (gum-trag’ah-kanth) A natural gum, soluble in hot water, used for holding small parts of jewelry together in preparing for soldering; sometimes added to borax-and-water flux for the same purpose. Also used as an adhesive for holding ground enamel to metal before firing.
gunmetal finish – A deep blue-black finish used on watch cases, jewelry, etc., produced usually by electroplating a coat of iron on the work, then coloring the iron in a chemical bath.
gut pallet – A silent escapement using gut across a cage-type anchor for the pallets similar in effect to a pin-pallet escapement.
gypsum – (jip’sum) A soft hydrous calcium sulphate, number two on the Mohs hardness scale, but commonly used in decorative carvings, currently in orange, satin spar figures from the USSR. Alabaster is a variety of gypsum, as is much satin spar. “Alabastra” of the ancients included calcite, as well as gypsum. The name alabaster was derived from the Greek name for an Egyptian town. It is usually white or light colored, but is often dyed many bright colors. See ALABASTER; ATLAS SPAR; SATIN SPAR; SELENITE.
gypsy setting – Usually refers to a complete one piece mounting consisting of a round shank running into a heavy top. The diamond or other precious stone set in the top is held in place by burnishing or hammering the metal over the entire girdle of the stone.
gyration, radius of – In a watch balance, the mean distance of the effective weight of all parts of the balance from its center of rotation.
H – The chemical symbol for hydrogen in a formula, but in referring to gems, it usually means “hardness.” See HARDNESS.
habit – Crystallography. The overall appearance of a crystal; for example, an elongated beryl crystal is said to have a prismatic habit, the usual diamond crystal to have an octahedral habit. Fluorite is sometimes octahedral and sometimes cubic in habit.
hack-saw – A frame saw for rapid cutting of thick metal, of heavier construction than a jewelers’ saw, used with teeth of blade pointing forward instead of toward the handle.
hack watch – 1. Any watch whose balance can be stopped to be synchronized with an accurate time source. 2. A watch used between ship and shore in seaports, for setting marine chronometers to time from an accurate clock on shore.
haematite – A British spelling of hematite.
haft – The handle of a knife or tool.
hailstone – A ball bort, found especially at Bultfontein, which is composed of alternating layers of gray and clear, poorly and well-crystallized diamond.
hair – A type of inclusion in a gem, resembling a hair. It may be due to the presence of a slender needle-like crystal or of an etched tube, as sometimes seen in kunzite.
hair amethyst – Sagenitic amethyst; black needles in this type of material coming from Montana are tourmaline.
hairspring – A metal spring of spiral, helical, or combined form, attached to balance of a watch, to govern its motions; the balance and the spring together constitute the “balance-assembly,” which is the true timekeeping element. See BREGUET HAIRSPRING; FLAT HAIRSPRING; HELICAL HAIRSPRING.
hairspring tweezers – See HAND-MADE TWEEZERS.
hairspring vibrator – A device for holding blank hairsprings while counting beats for selecting a spring to match balance with train; the vibrator usually comprises a standard-beating balance for comparison with the beating of the spring being tested.
hairstone – See SAGENITE.
half-and-half solder – Trade term for soft solder of the alloy, half tin and half lead, used for average work. For special purposes, involving certain contacts, etc., this formula may be varied, using more lead or more tin. See SOFT SOLDERING.
half-bored pearl – pearl drilled only partly through for use as pendant rather than as a bead.
half-brilliant – diamond cut without a lower part, the top brilliant cut, the bottom, one large culet. In a sense, it is a rose with a brilliant cut. See ROSE.
half-chronometer – term used in England meaning a highly adjusted pocket watch with lever escapement.
half Dutch rose, half Holland rose – A rose-cut stone with 18 triangular facets in the crown. See HOLLAND ROSE; ROSE.
half-dead-beat escapement – A clock escapement with its recoil, a compromise between dead-beat and full-recoil beat.
half-hunter – A watch case of the hunting type, with a glazed opening in center of lid through which parts of the hands are visible, with numerals enameled around the circumference of the opening. This kind of watch case has its greatest popularity in England. It is meant to combine the ruggedness of a hunting case with the convenience of open-face case. See DEMI-HUNTER
halfmoon – A fancy diamond shape, the girdle outline of which is semi-circular.
half-open tailstock – Tailstock for American type watchmakers’ lathe with upper half of spindle-hole cut away, to ease the motion of spindle for sensitive use in drilling; or to enable quick exchange of spindles for different uses.
half-pearl – A round pearl sawed in half. Also used to describe a Japanese culture pearl type, which is made from a pearl grown against the shell, instead of free, cut out and attached to a mother-of-pearl hemispherical bead of the same diameter, to make a perfect sphere. These pearls preceded the modern entire culture pearls. See MABE; CYST PEARL.
half-pearl work – In jewelry making, the setting of small, hemispherical pearls close together, in circles, curves, or other designs, set in flat-bottomed recesses, the upper corners of which are usually pressed or beaded inwards to fasten the half-pearls.
half-round file – A file whose cross-section has one flat and one convex face, gradually larger from point to tang.
half shell – The portion of a cylinder in cylinder escapement that forms the lips which act as pallets. See CYLINDER ESCAPEMENT.
half-timing – Running a lever escapement watch without the hairspring in place. Reversal of balance motion is effected by rebound of the roller jewel from outside the fork-horn; the long arc of balance motion required to do this is taken as indication of good adjustment of escapement.
Halifax moon clock – Clock showing lunar phases with the turning of an actual globe, half blue, half white, showing in an aperture, instead of the usual moon disk.
Haliotis pearls – See ABALONE PEARL.
Hallmarking Association – International organization of administrative members of state-recognized hallmarking authorities for precious metals (bureaux de garantie)’, established in 1965, to promote uniformity, protect hallmarks (poincons de garantie) from forgery, and further international cooperation in hallmarking.
hambergite – A rare beryllium borate found in colorless gemmy crystals in Madagascar. It is interesting only to collectors of rare gems, but has a very strong birefringence, which is exceeded among the gems only by sphene and cassiterite. The refractive index ranges from 1.553 to 1.631, but the dispersion is low and a cut gem resembles rock crystal.
Hamilton metal – A brass alloy made of equal parts of copper and zinc, long used as an imitation of gold.
hammer – In metalwork, a device for beating metal. In jewelry and silversmithing hammers are used for forming, stretching, embossing, raising, riveting, planishing, peening and chasing.
hammer, ball peen – Hammer with polished, rounded head used for peening, hardening or decorating metals.
hammer crank – Lever on arbor through which power is transmitted from striking train of a clock to raise hammer from bell or gong.
hammered – A form of metallic decoration obtained by repeated taps on the surface with a small hammer. See HARDENING.
hammer-hardening – Horology. Operation for making brass springs, in clock work, stiffer and more resilient, by hammering on anvil to condense the grain of the metal.
hammer-pallet – In a repeater watch mechanism, the tooth that raises the hammer by pressing on the hammer-tail. Baroque-shaped like the head of a hammer.
hammer tail – The rear ex tension of a pivoted hammer in a striking clock acted upon by the hammer spring.
hand buff – A stick covered with emery paper, or felt or leather charged with abrasive powder, or a solid abrasive slip, for light grinding and polishing operations in jewelry work and horology.
hand drill – One of a class of drills used in jewelry work and horology, including a drill-point in a spindle driven by a bow, a torsion cord, gearing, or a helical thread on a spindle engaging a sliding nut for rotating the drill.
hand-feed sliderest – A sliderest for a watchmakers’ lathe, to hold and operate a cutting tool, operated by a handcrank instead of by a shaft geared to the lathe spindle. See SCREW-CUTTING SLIDEREST.
hand-filled print – In the decoration of dinner-ware, a combination of decal and the design is applied by decal and the colors are filled in by hand.
hand painting – The design is applied by decal and the colors are filled in by hand.
hand gauge – A plate with linear markings for length as well as with a tapered needle to determine hole sizes of watch hands.
handless watch – Watch with dial on which time is shown by numerals appearing in openings in the dialplate; the numerals are on rotating discs under the dial.
hand-made – It is an unfair trade practice to represent that a product is hand-made or hand-wrought unless its entire shaping and forming from raw materials and its finishing and decoration were accomplished by hand labor and manually-controlled methods which permit the maker to control and vary the construction, shape, design and finish of each part of each individual product.—From Rule 11, Federal Trade Commission, Trade Practice Rules for the Jewelry Industry.
hand-made tweezers – A trade term meaning tweezers of fine steel and workmanship, especially sensitive and firm-gripping, used for hairspring work instead of for ordinary handling of watch parts. It is characteristic of hand-made tweezers that they are not electroplated, but show the natural surface of the hardened and tempered steel.
hand-pressed glass – Glass that is individually formed in a mold, by means of a plunger forcing the glass mixture into the desired shape.
hand remover – Tools for taking hands off watches, of various forms but all working on the principle of a pair of wedges to exert force without damaging dials or hands.
hand-rest – On a watchmaker’s lathe, an adjustable rest to support a cutting tool for hand-turning, distinguished from the sliderest with its mechanically operated cutting tool; also called a T-rest. See SLIDE-REST.
hands – The pointers that turn around the dials of timepieces, indicating hours, minutes and seconds. Early clocks and watches had only an hour hand; the concentric minute hand was introduced shortly after 1650; and the seconds hand about 1700.
hand-setter – An item of clock material; a split tube with a knob on one end, placed permanently on the time and alarm hand arbors of alarm clocks for setting the hands.
hand-spring – A spring on’ the minute hand arbor of English and Colonial American clocks, bearing against the under side of the minute wheel; overcoming its tension permits setting of the clock hand to time.
hand tongs – Special form of pliers, with graduated holes, for holding watch hands while filing or broaching holes larger.
hand-train – English term for dial train.
hand vise – A small vise similar to a bench vise but with its elongated base set into a handle.
handwheel – On the American-type watchmakers’ lathe, a wheel on the draw-in spindle for tightening chuck on work.
hand wrought – A term used to indicate that an article, so stamped, is made and decorated from a flat sheet of metal entirely by hand tools without the aid of machinery.
hard enameling – A class of enamelwork used decoratively on jewelry, watch cases, etc., and for numerals on timepiece dials, in work of the finer grades. Characteristic of hard enameling is that the work and the pulverized applied enamel must be brought to a high heat for flow and adherence. The enamel is a species of glass, usually colored; after it is melted on the work, the surface of the enamel is usually ground and polished. See ENAMELING.
hardening – A method whereby tool steel is heated to cherry red, approximately 1400°F, and quenched in water or oil. Steel so hardened is too hard for most purposes, so it is then tempered to the hardness and toughness desired. 2. Other metals may be hardened by alloying or hammering.
hard mass – An unusually hard glass used in imitation gems. Erroneously applied to synthetic spinel.
hardness – In reference to gems and minerals, this is defined as the resistance offered to abrasion or scratching. It is of great importance in gems, for their durability depends in large measure upon their hardness. See MOHS SCALE.
hardness pencil – A pointed instrument containing one of the minerals of the Mohs scale, used in testing for hardness by scratching.
hardness scale – See MOHS SCALE.
hardness wheel – An instrument for testing hardness, like the pencils, but with the points set like spokes in a wheel, a form in which the hardness pencils are frequently used by jewelers.
hard platinum – Alloy usually of pure platinum and 10 per cent iridium, used for jewelry, etc., as being more wear-resistant than soft pure platinum. Since World War II, 5 per cent ruthenium has been used as a hardening agent. Other hardeners have been suggested such as osmium.
hard soldering – Classification of soldering operations in which parts to be joined must be heated red-hot to fuse hard metal used as solder, making a stronger union than with softer solders fused at a lower heat. See SOFT-SOLDERING.
Hardy’s balance – Balance invented about 1800 by William Hardy and used in marine chronometers, characterized by high vertical attachments to the balance designed to reduce middle temperature error.
harlequin opal – A precious opal characterized by broad, sharply demarcated flashes of varying hues, often separated by a more or less well-defined border.
harmonic motion – The tendency to assume motion by objects of the same natural frequency, mass or active length when influenced by others. Example: When a descending weight nears a clock pendulum, it may swing in a direction opposite to that of the pendulum.
harp handle – A type of handle used on presentation cups of Irish origin. The handle resembled a harp.
Hartnup’s balance – A mid-19th Century chronometer, split-arm balance but with continuous spokes terminating in an inverted bezel-rim, designed to reduce middle temperature errors.
hatchet stone – Nephrite. See AXE STONE.
Hauynite, haiiyne – (ha’win-ite) An isometric sodium aluminum silicate, containing some sulphur; lapis lazuli can be regarded as a variety of this mineral. Named for the Abbe Rene Just Hauy, a famous French mineralogist of the late 18th and early 19th Century. See LAPIS LAZULI.
hawaiite – A pale green chrysolite or peridot found in Hawaii. See CHRYSOLITE; PERIDOT. Its use is highly undesirable, for not only is it a word of no significance in this relation, but it also tends to be confused with a particular type of basalt which has been named hawaiite by petrographers.
hawkbill – Heavy, curved-nose pliers used by silversmiths to hold work being beaten to form on bench block, etc.; also lighter pliers used in jewelry work.
hawk-eye – A variety of quartz containing parallel bluish-green needles of amphibole. When cabochon-cut, the gem exhibits chatoyancy. See TIGER EYE.
haystack – An American name for a high-domed button pearl.
head – The upper portion of a ring, mounted or to be mounted on a shank. It consists generally of a tapered box having prongs or other means of fastening a stone.
header – Punches in a staking set, for making rivets on turned countersunk shoulders, or on end of fitted rivet blanks.
headless screw – A set screw with the slot cut into the top of the threads without a head such as a side, dial screw.
headstock – On a watchmakers’ lathe, the attachment to the bed that contains the bearings for the spindle that carries the work. See TAIL-STOCK.
heart cam – Cam in the form of a heart; invented by Adolphe Nicole, 1862. Used in chronographs; the cam, attached to the arbor carrying the hands, causes them to return to zero when a “hammer” strikes the cam.
heart-shaped brilliant – A variation of the brilliant related to the pendant-cut brilliant, with the round end flattened, and the girdle broadened until its length about equals its breadth. Cullinan 5 was cut in this way.
heart-shaped emerald – A variety of the emerald cut.
heat-and-cold adjustment – In watches, the exact distribution of weight around the balance rim, to effect compensation for changes in the timing rate that are caused in the hairspring by changes in atmospheric temperature.
heated stone – A stone that has been treated by heat to change its color, at the mine or, after cutting, in electric ovens with the stones embedded in sand. The temperatures and precise methods frequently are regarded as trade secrets. Some white chalcedony becomes carnelian; amethyst and smoky quartz become citrine; some greenish yellow, greenish blue or brownish yellow beryl becomes aquamarine; some reddish brown topaz becomes pink to violet pink; some dark green tourmaline becomes light green; brown zircon becomes blue, golden brown or colorless; some tanzanite achieves a rich blue. No simple tests exist for detecting such heated stones.
heat shield – Trade name for a heat-resistant substance that prevents heat from reaching protected areas. Eliminates the need for removing stones while soldering.
heat-tinting – The gradual building up of a film of oxide on steel by heating to produce various colors as a finish, rather than for working temper. Mainsprings are always first tempered blue; but sometimes then de-colored and reheated to produce shades of brown or purple, for appearance sake; this is heat-tinting, as distinguished from tempering. See HARDENING; TEMPERING.
heat-treatment – 1. Metallurgy. A term broadly covering all operations for the purpose of altering the nature and conditions of metals for various uses; for example, hardening steel; tempering steel; annealing steel; case-hardening, etc. See ANNEALING; HARDENING; TEMPERING. 2. Gemology. See HEATED STONE.
heavy – A quality grade of sterling silver flatware offered by many American silversmiths until introduction of the place setting in the Nineteen Thirties. Heavy sterling flatware was in terms of 12 Troy ounces of sterling silver per dozen teaspoons. See MEDIUM; LIGHT.
heavy gold electroplate – A coating or plating, affixed by an electrolytic process, of gold or of a gold alloy of not less than 10 karat fineness, the minimum thickness throughout of which is equivalent to 100 millionths of an inch of fine gold. 2. Watchcases. Watchcases electroplated with gold or gold alloy to a minimum thickness of 11/2/1000 of an inch or greater are marked “Heavy Gold Electroplate,” preceded by designation of karat fineness of the gold alloy. Example: “16 Karat Heavy Gold Electroplate.” See GOLD ELECTROPLATE; KARATCLAD.
heavy liquids – High density liquids, such as bromoform and methylene iodide, which are used in the determination of gem stones by noting whether the gem in question floats or sinks in liquids of known specific gravity.
heel – 1. The back corner of the lifting plane on a club tooth of an escape wheel of a lever escapement. See CLUB TOOTH; ESCAPEMENT. 2. The angle formed on the bottom of a graver, at the cutting end of the tool to control the depth of an engraved line.
heel ball – Soft black wax used for filling engraved letters and numerals on clock dials, inscription plates, etc., by rubbing in the cold wax; used where heating for harder enamels would spoil finish on work.
height gauge – 1. Part of a watch crystal gauge that measures the vertical space inside the crystal for clearance for hands. 2. A measuring instrument for determining lengths of shoulders, etc., on arbors in watchwork.
heishi beads – (hee’she) Small oceanic shells strung as beads through a center hole that may be natural or drilled, offered in a variety of natural or dyed hues; simulated, also, in plastic. Used in costume jewelry in the U.S. after 1974.
helical gears – Pinions with leaves set at an angle with the axis; used in Swiss-type music boxes, and in “worm-gear” escapements.
helical hairspring – A balance spring with coils wound in the form of a cylinder instead of a spiral, used mostly in marine chronometers.
heliodor – An undesirable name for yellow-green beryl. Originally proposed for the beryl from Southwest Africa, it proved impossible to show that it was any different from any other beryl of this hue; the simple descriptive term is less confusing and preferable.
heliolite – Sunstone. Also see AVENTURINE,
heliotrope – Bloodstone; this name refers to an ancient legend that the reflection of the sun in water in which this stone had been placed was turned red, hence, “sun turning.”
hemachate – Said to be a light-colored agate spotted with red jasper, and also known as blood agate. It is an improbable looking word for English and seems to be the result of a confusion of languages. Hemagate would be more likely and equally unnecessary.
hematinon – (he-matt’i-non) A dark red glass used in the earliest times and said to be a stage in the preparation of aventurine glass. Also known as purpurin.
hematite – (hemm’-ah-tite) An oxide of iron and one of the principal ores of that metal. It may be hard and black and opaque, when it is sometimes used as a gem, or it may be soft and bright-red, when it makes a pigment, especially in paints. Even the blackest material gives a red streak when scratched across an unglazed porcelain tile, hence, the name given by the ancients, “bloodstone,” now no longer applied to this mineral. Also very wrongly called black diamond. See ROUGE; ALASKA DIAMOND.
hemimorphite – A silicate of zinc and a common constituent of oxidized zinc ores. Formerly known as calamine, great confusion has resulted from erroneous interchange of that name with smithsonite, the carbonate of zinc, and this new name has been substituted. The mineral crystallizes in orthorhombic crystals which are different at the two ends, or “hemi-morphic”; as in tourmaline, heating charges one end positively and the other negatively. Gemologically it is probably of interest only to collectors or as a constituent of a smithsonite-hemimorphite mixture. Colorless when pure, yellowish and bluish-green pieces have been found suitable for cabochon cutting.
Herapathite – The active constituent of polaroid, named for the discoverer of the quinine iodo-sulphate, W. B. Herapath, who, in 1851 first made the compound, but who was unable to put it to practical use.
Hercules stone – Lodestone.
Herkimer County diamonds – Misnomer for rock crystal from Herkimer County, New York. Small brilliant colorless crystals are found in pockets in a dolomite and have been widely distributed, usually uncut, under this name, which, while it probably deceives no one, is highly undesirable usage.
hermaphrodite calipers – A caliper which can measure both inside and outside diameters.
hertz – A frequency unit equal to cycles per second; symbol: Hz. Example: megahertz, one million cycles per second.
hessonite – (hess’on-ite) The proper name for the yellowish to reddish-brown variety of grossular garnet, derived from a Grecian word for “less,” which refers to its hardness in relation to the brown zircon, hyacinth, with which it is perpetually confused. It commonly has a granular internal structure which is visible through a lens. Often found in Ceylon, in association with zircons, also in California. Known as Ceylon hyacinth, false hyacinth and more commonly as cinnamon stone or essonite.
hexagon – A gem shape, a square hexagon is equi-dimensional while the blind hexagon has two parallel shorter sides, and the pointed has two parallel longer sides.
hexagon cut – A six-sided facetted cutting.
hexagonal system – One of the most important crystal systems, the four axes of which are located as follows: three of equal length in one plane, to each other; the fourth at right angles to this plane and longer or shorter than the other three. Many gem minerals crystallize in this system and its various classes, beryls, corundum and quartz among them.
hexagon tip – An item of jewelry findings; a hexagonal metal cup, with a ring on its closed top for a necklace or other clasp; the cup to hold the end of a chain or cord soldered or cemented in. See FINDINGS.
H.G.E. Abbreviation for heavy gold electroplate.
HI – Abbreviation for “heavily included.” See CLARITY GRADE.
hiaqua – Necklace of strung shells or beads, of American Indian style.
hiddenite – (hidd’n-ite) A green variety of spodumene, found only in North Carolina in small crystals, the coloring of which is caused by minor amounts of chromium. It has not yet been shown that paler green spodumenes from Brazil and Madagascar are colored by chromium and so entitled to this name, any more than greenish beryl, colored by iron, can be called emerald.
high brass – Brass of high tensile strength, 66 per cent copper and 34 per cent zinc, used for gear-wheels and other parts of watches and clocks. See LOW BRASS.
high frequency – 1. Electricity. An alternating electric current of high frequency, more than 20,000 cycles per second; a source of power used in modern furnaces for efficient melting of metals. 2. Horology. When referring to a balance watch, those beating faster than 8 times a second (28,800 VPH or 4 Hz); the faster-moving train is less influenced by jolts, gravity and poise errors, and may be regulated to close limits.
high relief – Ornamental work on jewelry, etc., in which designs are formed standing well out from the background surface. See LOW RELIEF.
high speed steel – Steel of great hardness and toughness containing a high percentage of tungsten, retaining its cutting ability even when red hot; thus able to cut objects at high speeds.
Hindu cut – Said by Schlossmacher to be the cutting form of the Orloff, the principal requirement for which is that it should retain as much size and weight as possible, without regard to symmetry requirements.
hinge-joint – One of the three or more pieces of metal tubing forming with a pin a hinge for a watch case, locket, etc.
hinge pearls – Baroque pearls which grew near the hinge of the mollusk; they are elongated and pointed at the ends.
Hinojosa topaz – Misnomer for citrine quartz from Hinojosa del Duero, Cordova, Spain.
Hipp trainer – A device for closing a contact-making switch in electric clocks of armature-driven pendulum type. A short, notched lever on the pendulum trails across a knife-edge on switch; when the pendulum arc has been shortened sufficiently, the notch catches on knife-edge, which is depressed to close the switch and give a fresh electro-magnetic impulse to pendulum.
hobbing cutter – A spiral gear-cutter in the form of a continuous thread used to cut gears and by its worm-like nature to rotate the gear blank as it cuts, obviating the necessity of indexing.
hock – Also called Rhine wine, for the serving of which it is intended; taller stemmed than the white wine or Port glass, and with a squatter bowl. Capacity: 5 oz., sometimes 6 or 7 oz.
hoek – The first four top and bottom facets in diamond cutting, after the table and culet are made.
hog-bristle regulator – An adjustable slide holding two stiff brushes vertically, against which the foliot (balance-bar) of earliest watches banked, to regulate its arcs of motion and produce a crude regulation of rate. From this, probably, arose the current fable that the earliest hairsprings were hog bristles bent into spiral form.
hole-closing punch – Steel punch with concave end, for reducing diameter of pivot holes in brass clock or watch plates that have become enlarged through wear.
hole jewel – The pierced jewel part of a cap-jeweled pivot bearing, as distinguished from the unpierced cap-jewel (the end-stone) that is set over the hole jewel to receive the end thrust of the pivot arbor. See CAP-JEWEL; END-SHAKE.
hole spar – Andalusite, variety chiastolite.
Holland rose or full Holland rose – A rose cut stone with 24 triangular facets and a large single facet on the bottom. Often attributed to Cardinal Mazarin, because he was the first to have any large stones cut in this way. See DOUBLE HOLLAND ROSE; HALF HOLLAND ROSE; ROSE. Also known interchangeably as Dutch rose.
hollow center – Required marking for a quality-marked article made of karat gold, if the article has a hollow center that might deceive a purchaser. Such an article may not be described as “solid.” -From Rule 22, FTC Rules for the Jewelry Industry.
hollow doublet – A doublet in which the lower side of the crown portion or the top of the lower section has been hollowed out and filled with a colored liquid. Rarely seen. See DOUBLET.
hollow fusee – Form of fusee with its upper pivot sunk in a recess, designed to reduce the thickness of watch movements. See FUSEE.
hollow pearls – Misnomer for an early type of imitation pearl, which consists of a hollow glass sphere, the inside of which is coated with the pearl essence, and then filled with wax to give it weight and opacity.
hollow pinion – Pinion drilled through its entire length, as a Swiss center pinion for a friction-fit setting-arbor.
hollow-rim balance – Form of chronometer balance invented by Victor Kullberg, London, in 1885, with a pulley-like groove in outside of rim, to reduce the middle temperature error in temperature adjustment.
hollow ring-ball – In item of jewelry findings, a hollow ball with ring attached; used as a detail in assembling jewelry.
hollow-spindle lathe – Term used sometimes to differentiate live-center lathe from dead-center lathe. See DEAD-CENTER LATHE; AMERICAN LATHE.
hollow wire – Tubular gold or gold-filled stock used for making bracelets and other jewelry.
hololith ring – Term for a ring cut from a single piece of gem material. Jade, quartz and jasper are often so cut.
homogeneous compensation – Correction for temperature effects on tower clock pendulums, produced by a bar of metal that alters the position of a fork embracing the suspension spring, to shorten or lengthen the acting length of the pendulum by an amount equal to the changes in length of the pendulum rod occasioned by heat or cold.
Honan jade – (ho-nan’) Same as Soochow jade, another misleading name for soapstone or agalmatolite.
hone – A fine-grained natural stone (Ayrstone, bluestone, etc.) of slaty character, used in the form of a flat-faced lap, with water, for leveling and smoothing brass parts of timepieces preparatory to gilding.
honing – A modern process for finishing metal parts of machines, etc., in which abrasive action is applied to the work in a variety of directions, producing a surface super-smooth and accurately to form.
hood – 1. The part of the case of a long-case clock, or Dutch type wall clock, that covers the movement; removable by sliding forward or upward, for access to the movement. 2. A compartment with sliding, transparent front and an effective exhaust for removal of dangerous gases when refining metals.
hook, barrel – The slight extension on the inside of the barrel wall to which the mainspring is hooked.
hooked graver – A hand-turning tool, its cutting part formed as a projection to cut a seat in the barrel for the cover; or for cutting on the bottom of the barrel without altering the mainspring hook, etc.
hook escapement – Common name for virgule escapement, developed to its final form by J. A. Lepine, Paris, about 1780, as an improvement on the cylinder escapement; it did not fulfill his hopes because of its inability to retain oil on its acting parts.
Hooke’s law – A principle in mechanics discovered by Robert Hooke, basic to the action of hairsprings and other springs in horology, which he stated in Latin: ut tensio sic vis (“as the tension, so the force”); i.e., in an elastic material, strain is proportional to stress; the value of stress at which a substance ceases to obey Hooke’s law is known as the elastic limit. See HOOKE, ROBERT.
hook-piece – English term for a gathering pallet, that operates in connection with a rack in striking watches and clocks. See HOUR RACK; HOUR SNAIL.
hoop – The ring part of a finger ring. See CHATON.
hoop wheel – In clock striking work, a disc with a notch for a detent to stop the train at a position to allow the warning pin wheel to make a portion of a turn before beginning the striking of next hour.
Hope Star – Synthetic star sapphire produced in many colors by Wiedes Carbidwerk in Freyung, West Germany. It was introduced almost simultaneously with the Linde Star produced by the Union Carbide Corp; its production continued after Union Carbide suspended output of Linde Stars. See LINDE STAR.
Horatio diamond – Misnomer for rock crystal from Arkansas.
horizontal escapement – The cylinder escapement. “Horizontal” was applied as an early descriptive term, because the escape wheel is in horizontal plane with movement plates, whereas the earlier verge escape wheel is at a right angle or vertical to the plates; the change of term from “horizontal” to “cylinder” came about gradually after the verge or “vertical” escapement went out of use and when all escapements then had horizontal escape wheels, requiring a new term to differentiate the horizontal-cylinder escapement from the others. See CYLINDER ESCAPEMENT.
horizontal positions – In adjusting watches to positions, the “dial-up” and “dial-down” positions of the watch during timing.
horloge – (or’-loje’) French term for any device that measures time; a clock.
horn – A gem shape, a thin curving triangular piece.
horn anvil – Anvil for watchmakers’ and jewelers’ use, with a projection of pointed form to enter small openings for riveting and forging operations.
hornblende – Loosely used for the amphibole series, it is a member of that series, dark in color and without gem use, See AMPHIBOLE.
horns – On the fork of a lever escapement, projections on each side of the fork slot, for providing safety-action during unlocking and impulse. See FORK.
hornstone – A fine-grained variety of quartz, named from the similarity of appearance of some of the material to cow horn. It has a splintery fracture and grades into chalcedony and jasper. In color it is gray, brown, yellow, green or black. Schlossmacher includes apricotine and jasper as varieties. Today only attractively-colored pieces are cut; these would now be called jasper, so it is no longer of any gem significance.
Horological Institute of America – Organized in May 1921 by National Research Council, Washington, D.C., to relieve the shortage of watchmakers and award certificates of proficiency. Succeeded in 1960 by American Watchmakers Institute.
horologist – One who practices horology; especially, one who is learned in theory and highly skilled in practice of horology.
horology – The science of time measurement, including the art of designing and constructing timepieces.
Hot Springs diamond – Misnomer for rock crystal from Hot Springs, Ark.
hour angle – Angle, measured in hours, minutes and seconds of time, which the declination circle of a star or planet makes with an observer’s meridian, at the celestial pole. See NAVIGATION; TIME DETERMINATION.
hourly controller – Mechanism for automatically setting a clock to correct time every hour by an electrical impulse on a circuit wired to an accurate clock at a central station. This system differs from master and secondary clock systems in that the clocks controlled are each a self-driven unit, instead of dependent for motion on current from central clock.
hour rack – In striking clock work, a toothed metal arc, one notch of which is picked up by the gathering pallet for each hour struck. See HOUR SNAIL.
hour snail – In striking clock work, a disc on the hour-wheel, its rim cut into 12 steps, to govern the number of strokes for each hour, by stopping the tail-pin of the rack when the latter is released at each hour.
hour star – The star wheel upon which the snail of a striking clock or watch is used to “flirt” and position the wheel into the next hourly phase. Used when snail is not positioned directly on the hour wheel.
hour-wheel – The gear-wheel in the dial train of a timepiece which is turned by the minute pinion, and on which is attached the hour hand.
hour-wheel pipe – A tubular extension on the hour wheel, surrounding the cannon pinion, extending through the central hole in the dial, and carrying on its outer end the hour hand of a timepiece.
hub – 1. The central part of a wheel. 2. Fixed arbor on which winding wheel turns. 3. Arbor for the barrel in a motor barrel.
hulls – Thin nacreous layers of pearl.
humidity error – A slight slowing of rate in marine chronometers, due to increase of moisture in air.
humper – Tweezers or pliers with jaws formed to bend guard-pin forward or backward for adjusting guard-shake in lever escapement. See GUARD-SHAKE.
Hungarian cat’s-eye – A greenish quartz with fibrous amphibole inclusions from the Bavarian Fichtelgebirge.
Hungarian opal – Precious opal with a white, milky ground color and lively small flecks of violet-blue, green and red. The Australian opal production has displaced the Hungarian (Czechoslovakian) in the world market, and little is now mined.
hunting case – A watch case on which the dial is covered by a lid that may be thrown open by pressing a button on the pendant; differentiated from open-face case, in which the dial is covered only by a glass or crystal.
hyacinth – (hi’a-sinth) Properly applied to orange, red and reddish-brown zircon, also used not unjustifiably for yellow and brown zircon. Its use for hessonite is erroneous and confusing, as are false hyacinth, oriental hyacinth, and Ceylon hyacinth.
hyacinth of Compostella – Opaque, brick red, doubly terminated quartz crystals from the gypsum beds of St. Jago of Compostella.
hyalite – (high’ah-lite) A clear colorless opal, also called water opal or Mutter’s glass. Of no gem significance.
hyalithe – A strong opaque glass resembling porcelain, in red, green, black, brown, etc.
hydrocarbon – A liquid such as carbon tetra-chloride, tetrachlorethane, or benzine, used as a degreaser.
hydrochloric acid – Also called muriatic acid. An aqueous solution of hydrogen chloride gas, used in jewelry work and horology for many purposes. A mixture of one part nitric acid and three to four parts hydrochloric acid dissolves gold or platinum; hydrochloric acid is used for removing temper-colors from steel, etc. See AQUA REGIA; TEMPERING.
hydrofluoric acid – An aqueous solution of hydrogen fluoride, used for etching glass, enamel, etc.
hydrogen furnace – An atmosphere-free furnace in which the metal heated is not subject to oxidation. This enables metals to be soldered without the use of a flux and to emerge from the furnace clean and free of discoloration.
hydrophane – (high’dro-fane) A variety of brownish, yellowish, or greenish opal which absorbs large amounts of water and becomes almost transparent. Upon drying out it again becomes opaque; the effect can be repeated indefinitely. It is of gem interest only because of this property and little used. Some reddish Mexican opal is of this type and is easily detectable because of the way it clings to the tongue.
hydrostatic weighing – Determination of specific gravity of the substance of an object by weighing it immersed in water, subtracting this weight from its weight in air, then stating the specific gravity as the ratio between (A) the weight in air, and (B) the difference found by the subtraction.
hydrothermal – Literally, high-temperature water; refers to the process of stone synthesis by vapor (superheated steam) transport of material to a growing crystal. Quartz crystals and Linde synthetic emeralds have been grown commercially by the hydrothermal process. Other stones, rubies and zincite, can be grown this way, but are more costly than those made by simpler methods. See FLAME FUSION and FLUX FUSION.
hygrometer – Instrument for indicating amount of moisture in air; sometimes used in astronomical clock vaults along with barometer, for controlling atmospheric conditions affecting timekeeping of clocks.
hypersthene – (high’pers-theen) A variety of pyroxene, dark brown or green to black. Sometimes showing a metallic schiller luster and cut cabochon for collectors to give cat’s-eyes, but of no real gem significance. See PYROXENE.
hypocycloid – The path traced by a circle rolling within another. The shapes of the flanks of pinion leaves in watches and clocks are de¬rived from hypocycloids. See EPICYCLOID.
I – Abbreviation for “imperfect,” “inclusions,” or “included,” in diamond clarity grading.
IC – Abbreviation for INTEGRATED CIRCUIT.
Iceland agate, Icelandic agate – Erroneous name for iridescent gray or brown obsidian. See OBSIDIAN.
Iceland spar – Colorless, flawless calcite. Used in Nicol prisms for polarizing microscopes and in dichroscopes. For many years a cave in Iceland was the only source of this material, hence the name.
ice spar – A colorless sanidine and a confusing alternate name for moonstone.
ichthyopthalmite – (ik-thee-ahf thai-mite) A fancy name for apophyllite, the English equivalent, “fish eye stone,” for this Greek root word having already been used for other things.
icy flakes – Small internal cracks often present along twin boundaries, but sometimes developed within a diamond by overheating on the polishing lap. Icy is sometimes a term for a natural frosted surface on a diamond, like artificially burned stones.
Idar agate – (ee’dar) An agate found near the German gem-cutting center at Idar-Oberstein. This occurrence was the fundamental cause of the growth of the industry at that spot. In general they are colorful but smaller agates, not to be compared with the Brazilian-Uruguayan agates of today.
Idar-Oberstein – Gem-cutting center in the picturesque Nahe river valley, southeast of Mainz, Germany. Several hundred plants polish, drill or engrave colored stones; others cut diamonds. These skills originated with the cutting of local agate, amethyst and jasper in the XVI Century.
I.D.B. act – The Illicit Diamond Buying Act, a South African law against unlicensed trade in diamonds.
identification bracelet – Bracelet formed by a curved center plate and flexible ends, the center plate being monogrammed or showing identity of wearer; introduced in World War II.
idiochromatic – (id”ee-o-kro-mat’ic) Mineral coloration due to essential elements of the composition of the mineral rather than to chance impurities; the pigments of most gems. Turquoise and lazulite are examples of idiochromatic gems. See ALLOCHROMATIC.
idle wheel – A wheel in a gear-train that does not affect the ratio of turns, interposed to change direction of motion, or to accommodate a distance of centers that would otherwise be wrong for the required ratio of turns. See CENTER DISTANCE.
idocrase – (eye’doe-kraze) VESUVIANITE.
igneous rock – (igg’nee-us) One of the three great classes of rocks, and the most fundamental of all. Igneous rocks are those which have formed as the results of the solidification of a molten magma. Granite and basalt, pegmatite dikes and diamond pipes are examples of igneous rocks and formations. See SEDIMENTARY ROCKS; METAMORPHIC ROCKS.
illam – The sedimentary gravel deposits of Ceylon in which rubies and sapphires are found.
illusion setting – A prong setting distinguished usually by a narrow ring of metal surrounding the girdle of the diamond. The ring or rim is provided to diffuse the sharp outline of the stone, thereby creating an illusion that the stone is larger than it actually is.
ilmenite – A slightly magnetic, black iron titanium oxide, resembling hematite, occasionally cut as a gem for collectors. It can be distinguished from hematite by the brown streak it leaves upon an unglazed porcleain tile, in place of hematite’s red streak, and by its stronger response to a magnet.
imitation gem – A material resembling a gem-stone that does not have both the composition and the structure of that gemstone. It usually refers to glass, bakelite or other plastics which have compositions differing greatly from the gems they simulate, but it is also used to describe natural stones so treated as to simulate more-precious ones, e.g., German lapis (jasper dyed to resemble lapis lazuli). Glass commonly used to imitate a diamond consists of 300 parts of quartz, 470 of red lead, 163 of potassium carbonate, 22 of borax and 1 of white arsenic; manganese, cobalt, copper, iron or chromium pigments are added to simulate purple, blue, red, yellow-to-green, and green and red stones respectively. Glass imitations have a hardness of 5 to 6; are singly refractive and therefore do not show dichroism; have a refractive index of 1,50 to 1.80; a specific gravity of 2.5 to 4.0; usually include air bubbles, and are warm to the touch. See GLASS; RHINESTONE; BRILLIANT; CHATON; PASTE; STRASS; AVENTURINE; YAG. Bakelite, a phenolformaldehyde plastic, is used to simulate both transparent and opaque gemstones, but plastics are so different in physical and optical properties from the stones they imitate that they can easily be detected.
imitation compensation balance – A mono-metallic balance with rim half cut through from its top, used in cheap imported watches to counterfeit the true bimetallic compensating balance. See BALANCE.
imitation diamonds – Currently, numerous materials not found in Nature (and hence “synthetic” only in the broadest sense of the word) with high refractive indices and, sometimes, strong dispersion. See YAG; STRONTIUM TITANATE, TITANIA.
imitation material – Horology. Replacement parts for repairing watches, made by factories other than the manufacturers of watches in which the parts are to be used.
imitation pearl – A manufactured product that simulates pearl. Commonly, a transparent glass or plastic bead, thinly coated with synthetic pearl essence. Better and more expensive, a translucent white glass bead, thickly coated with essence d’orient, a solution of guanine from fish scales, polished and lacquered.
immersion method – Stone testing, A method of refractive index determination widely used among mineralogists, which essentially consists of immersing the unknown substance, in index of refraction, until the liquid and mineral are matched. See INDEX OF REFRACTION.
Imori stone – Imitation stones made in all colors from devitrified glass, with some crystalline structure, by a Japanese scientist. An imitation jade of this material is also called “meta-jade.”
impedence – The seeming resistance of a circuit in an electrical timepiece to the flow of an alternating current.
imperfect – Abbreviated “I,” the diamond clarity grade at the bottom of a flawless-to-imperfect range. Stones of this grade contain inclusions and marks that are visible without magnification to a trained eye. Sub-grades 11; 12 and 13 are used, according to the number, location and degree of faults.
imperfection – Gems. According to U.S. trade practice, any flaw, crack, carbon spot, cloud or other blemish of any sort observable in a gemstone, when the latter is examined by a trained eye under a 10-power magnifier. See INCLUSION.
imperfection grade – See CLARITY GRADE.
imperial diamond – See GREAT WHITE DIAMOND.
imperial jade – A popular and trade term for the fine quality translucent, emerald green jadeite. See also JEWEL JADE and PRECIOUS JADE.
imperial yu stone – See YU. This variety is prized by the Chinese and is green aventurine quartz.
imperviousness – The ability of a watch case to withstand and exclude the entry of moisture under pressure (water-resistance).
impression pad – A pad made of printers’ gelatin, for quickly making reproductions of an engraved design on pieces of work to be engraved to match the original design. See TRANSFER PAD.
impulse – The act of applying power by an escapement to the balance of a watch or to the pendulum of a clock. An impulse is given at every beat in lever and cylinder escapements; at every other beat in chronometer-detent and duplex escapements; at every beat in dead-beat and recoil verge clock escapements and Riefler escapement; and at various longer intervals in other precision clocks. See ESCAPEMENT.
impulse arc – The portion of the circular motion of a watch balance during which the escapement is applying power to the balance; the remaining amount of motion is the “supplementary” arc.
impulse clock – One of the dial-units of a master-and-secondary clock system, in which the hands are moved, usually once a minute, by a ratchet and click driven by an electromagnet and armature given an electric impulse through a wired circuit from the master clock.
impulse face – 1. The inclined plane of the acting which escape wheel teeth press to produce the “lift” in escapement action. 2. The plane on the end of an escapement wheel tooth in club-tooth design of a lever escape-wheel.
impulse pallet – In a chronometer detent escapement and in a duplex escapement, the tablet of stone or steel attached to the balance arbor on which the escape-wheel teeth press in applying power to the balance.
impulse roller – In the double-roller lever escapement, the disc on the balance staff in which is set the roller-jewel to which power is applied by the fork, and thus through the impulse roller is power applied at each vibration of the balance to keep it going. The other roller in a double-roller escapement is the safety or guard roller. See LEVER ESCAPEMENT.
impulse spring – A suspension spring for the pendulum of precision clocks of the Riefler type, through which escapement impulses are imparted to the pendulum; the cradle to which the spring is fastened is rocked by a crutch attached to the pallets, this motion bending the spring sufficiently to maintain the momentum of the pendulum.
impulse tooth – In a duplex escapement, one of the vertical teeth on the web of the escape wheel that act on the impulse pallet, differentiated from the horizontal teeth that rest on the balance staff to provide locking between impulses.
in beat – The condition in a lever watch in which the hairspring, at rest, with no power on the escapement from the train, will bring the balance to a stop with the roller jewel standing exactly above the line of centers of the escapement, with the fork-lever in the center of space between the bankings; in a cylinder escapement, when in beat, the acting ends of the cylinder lips both lie on a line intersecting the escapement’s line of centers at right angles. A pendulum clock is in beat when the impulse is applied at equal angular distance on each side of the center of its arc of motion. An out-of-beat condition in a watch or clock is indicated by hearing it ticking at intervals alternately long and short, instead of in periods of equal length.
incise – To cut into or engrave so that a sunken line is produced.
incised – A term applied to the lines produced by a burin or graver.
inclination test – Taking the timekeeping rates of marine chronometers, with the instruments running in positions at an angle from the normal horizontal position of the dial which would normally be maintained by action of the gimbals; the gimbals are locked out of action during an inclination test.
incline – The acting edge of a tooth of an escape wheel in a cylinder escapement.
incline plane clock – An unpowered drum clock rolling slowly down an inclined plane. An inside counterweight acting on the train of gears supplies the restraining as well as motivating force.
inclusion – 1. Crystallography. Any evidence of interruption in crystal growth, including (a) protogenic, or pre-existing, inclusions-foreign solid matter or guest mineral present before the gemstone crystallized and trapped it; (b) syngenetic, or contemporary, inclusions, formed simultaneously with the gemstone— foreign minerals, drops of mother liquid, or gas bubbles that were encased within the growing crystal; (c) epigenetic, or subsequent, inclusions, occurring after the gemstone was formed—due to re-crystallization or penetration of outside substances along cracks and fissures.—After Dr. E. Gubelin. 2. Diamond grading. Inclusions, also called “internal characteristics,” for which polished diamonds are examined in clarity grading, include: cleavages, fractures, knots, bubbles, carbon spots, clouds, fezels, and bearded or feathered girdle.
inconel – A white gold imitation alloy.
incrustation – Decorative work consisting of the inlaying of ornamental material such as precious metals or stones in the surface of the article incrusted.
independent seconds – A type of chronograph in which the seconds hand is driven by a separate gear-train instead of by the regular time-train.
index pin – 1. On a watchmaker’s lathe, a thrust-pin engaging with the circle of holes on the back of a driving pulley, for dividing work into faces of holes to be filed, milled or drilled in definite angular relation to each other. 2. One of the pair of pins that embraces the outer terminal coil of a hairspring and connects it with the regulator.
index, regulator – The arm or hand of regulator of a watch, that moves over a graduated scale usually on top of the balance cock to judge the amount of regulation.
Indian agate – Moss agate.
Indian jewelry – Jewelry, characteristically silver set with turquoise, made by Indian residents of the United States. Members of the Navajo and Zuni tribes learned the art between 1850 and 1870 from Mexican blacksmiths and silversmiths of the Rio Grande valley, and soon were making bracelets, rings, necklaces, pins, hair and belt ornaments and other jewelry. Non-Indian manufacture of such jewelry began in 1910. Such jewelry not made by Indians may be called “Indian type,” “Indian style,” “Indian look” if the word “Indian” or designs associated with Indians are used in its promotion. See HAND-MADE.
Indian cat’s-eye – Chrysoberyl cat’s-eye.
Indian cut – A term for asymmetrically shaped gems, cut in India and Sri Lanka, designed to yield the maximum return (in weight) for the piece of rough. Most stones so imported are recut for Western tastes. All the standard cutting forms, such as brilliant, step, mixed and cabochon, are recognizable in these distorted native-cut gems.
Indian emerald – Misnomer for crackled green quartz.
Indian garnet – Almandine.
Indian jade – A misleading name sometimes applied to aventurine quartz.
Indian topaz – A name of many meanings, at best, a saffron yellow topaz, typical of the Ceylon gravel deposits, and at worst, citrine quartz, with yellow sapphire between the two extremes. See BRAZILIAN TOPAZ; KING TOPAZ.
Indian pearl – Oriental pearl.
India oilstone – Abrasive material manufactured in forms like laps, slips, wheels, etc., for grinding tools, shaping timepiece parts, etc.; a durable and fast-cutting material for the purpose.
indicator. – 1. A trueness-testing instrument for chucks or work in a lathe, with leverage mechanism for magnifying errors. 2. The hand on the setting-dial of an alarm clock.
indicator, winding – A device on precision watches and chronometers with pointer on dial to show the extent to which a mainspring is run down, to insure against forgetting winding the timepiece.
indicolite – Light or dark blue tourmaline, one of the rarer colors of the gem. Also known as Brazilian sapphire.
indigo sapphire – Very dark blue sapphire. See WATER SAPPHIRE.
indirect seconds – A center seconds hand not connected directly to the fourth wheel (which is not situated in the center of the watch). See DIRECT SECONDS.
inductance – The initial opposition of a conductor to a current.
induction motor – Type of alternating current motor used in electric clocks in which current in a primary winding induces current in rotor to produce rotation.
industrial diamonds – Diamonds usually unsuitable for gem purposes, because of flaws or poor color, and which are, therefore, used in industry because of their superior hardness over all other materials. Between 75 and 80% of all diamonds mined are so flawed or poorly colored that they are fit only for industry. Diamond saws, diamond drills and wiredrawing dies are among the uses to which such stones are put. BALLAS, CARBONADO and BORT are all industrial grades of diamond.
infrasonics – Below the perception of human hearing, in contrast to ULTRASONICS.
ingot mold – A mold, which, for jewelry work, is usually made of iron and with adjustable walls, to produce a variety of sizes of cast metal bars or ingots. The side walls are detachable, to facilitate removal of the ingot from the mold.
initial ring – A finger ring, worn mostly by men, with the initial letter of the wearer’s name made of metal set on a background of stone or gold of contrasting color.
ink-recorder – A form of chronograph or timer watch which makes an inked dot on a dial to record the time at which the hand is stopped.
inlay – 1. Type of decorative work used on wood clock cases, etc., in which thin, flat material, cut into a design, is sunk in a counterpart of the design cut in the surface of the article. Contrasting colors of metals, woods, ivory, etc., are used. 2. In jewelry, to embed a material in another substance so that the surfaces of each are level. Stones may be inlaid in metal, as can metals of contrasting colors.
inner-terminal hairspring – A balance spring of the Breguet or over-coiled type, which has also a definitely formed terminal curve in the coil nearest the hairspring collet, designed to work with the overcoil in improving the isochronal and position timekeeping rates of a watch. See CURVES; TERMINAL; ISOCHRONISM.
inoxidizable – The ability to withstand rust or tarnish such as stainless steel, gold, etc.
insert guard ring – A double ring, sometimes ornamented with gems, with a space between to accommodate another ring in its center. Together, they appear as one larger ring.
inside drop shake – In a lever escapement, the movement of the escape wheel during the time after a tooth has become disconnected from the lifting plane of the receiving pallet, until another tooth has come into contact with the locking-face of the let-off pallet See DROP.
inside graver – Engravers’ graver with bayonet-shaped or S-curved end, for cutting lettering inside of finger-rings, deep bowls, etc.
insulator – Horology. An outer-case made of soft iron lined with velvet or leather, enclosing a watch being worn, to protect it from magnetisation. Action is that magnetic currents flow through the iron insulator around the watch instead of through it. Silversmithing. Small pieces of heat-resisting substances (usually ivory) inserted in the handles of coffee and teapots to prevent the handles from becoming hot.
intaglio – 1. A form of work for decorative or other uses, in which a design is cut below a surface which forms the background for the design. 2. An engraved gem, of which the rim is the highest portion and the figure incised below it, either as a negative impression or raised above a depression in the center, and thus resembling a cameo. Coats of arms and monograms, subjects suitable for a seal, are common carvings in an intaglio, as well as the figures usually seen in cameos. See CAMEO.
integral balance – A balance for chronometers and precision watches, invented by Charles Ed. Guillaume of Sevres, France, with a bimetallic rim of brass and nickel-steel, which eliminates the middle temperature error. See MIDDLE TEMPERATURE ERROR.
integrated circuit – An electronic circuit made with semiconductors, used in solid state watches as a frequency divider, reducing the frequencies put out by the quartz crystal or other frequency standard. In solid state digital watches, it also decodes the time information, provides memory-recall services, and drives the display and other parts of the timepiece.
intermediate wheel – See IDLE WHEEL; INTERCHANGE WHEEL.
interference colors – Hues given off by a bire-fringent substance under examination, between crossed polarizing devices, in a polariscope or a petrographic microscope. Running the spectrum from gray to red and blue, the hues are caused by one ray being slowed more than another as they reunite after passing through the specimen into the second polarizer. Their hue and intensity may be used to judge the relative strength of birefringence; bright colors are referred to as first order colors; those slightly less intense as second order colors, and so on. If a stone is so highly doubly refractive that there is no hue, a polariscope or card test can determine whether it is doubly or singly refractive. See BIREFRINGENCE.
interference figure – A phenomenon observed in convergent polarized light with crossed nicols. Figures are useful in the determination of the optical character of unknown gems, and are fairly constant properties of any birefringent crystal.
internal gearing – Gear wheel with teeth inside its circumference, pointing toward the center, as in the escapement carriage of a tourbillion or karrusel watch. See KARRUSEL; TOUR-BILLON.
internally flawless – A clarity grade for cut diamonds that came into use during the early Nineteen Sixties; sometimes abbreviated “IF.” A diamond can only be defined as internally flawless when, examined by an experienced professional under 10-power magnification in normal light by means of an achromatic, aplanatic lens, it proves to be absolutely transparent and free from inclusions or internal characteristics—CIBJO. A diamond which has no internal characteristics but which, due to minor finish faults is not “flawless” and therefore cannot be designated FL or “flawless,” may be called IF or “internally flawless” provided the finish faults are so minute that they can be removed by a gentle polishing with an insignificant loss of weight only – Scandinavian Diamond Nomenclature.
internal stress – Gemology. Stress resulting from inclusions or other structural irregularities, visible, in singly refracting stones, like diamond, through the polariscope.
international lathe – A type of watchmaker’s lathe, with the bed made of a round bar milled flat on back side to keep attachments upright; a European modification of American-type lathe, designed to reduce manufacturing cost.
Interrupter – In electrical horology, a form of current breaker or switch.
interval clock – A precision clock for laboratory or manufacturing-process use, with buzzer or bell to signal elapsed time periods, for taking data in chemical or other experiments or operations.
intrados – The convex underside of an arch, as that of a clock case.
intumescence – (in’too-mess”sense) Fusing accompanied by bubbling, the result of some component escaping as a gas. Many gems melt in this way, though high temperatures are necessary to fuse them at all.
invar – An alloy of nickel 36 per cent and iron 64 per cent, which has a very low coefficient of expansion; used in horology for precision clock pendulum rods and integral watch balances.
inverted pendulum – A slow-moving, short pendulum effected by placing almost half its mass above the point of suspension such as used in metronomes and swinging ball clocks.
investing flask – Stainless steel tubes of different sizes used to hold investment molds for casting.
investment – A refractory material used to surround a disposable pattern, as of wax, and act as a mold for receiving metal which fills the cavities of the eliminated pattern.
iolanthite – (eye’o-lanth”ite) Local name for a banded reddish jasper found in pebbles in gravels of the Crooked River, in central Oregon.
iolite – (eye’o-lite) A magnesium, iron, aluminum silicate mineral which is sometimes used as a gem. It is interesting for its strong pleochroism; in the three pinacoidal directions it shows deep blue, light blue-gray, and yellow-white, respectively. Cut gems will usually show some of this pleochroism to the naked eye. Its hardness is about that of quartz, its specific gravity 2.6, and its refractive index about 1.55. It is found in a number of places, usually in metamorphic rocks, but only rarely is it possible to cut gems of more than a few carats. Also known as CORDIERITE and DICHROITE.
Ionic – Term designating one of the three orders of Greek architecture, distinguished by the spiral scroll-shaped ornaments of its capital. Candlesticks are often made in this style.
ionization – A process in which particles of a gas become carriers of electricity. The transformation of an atom into a positive or negative ion.
Iran lapis – Persian lapis.
Iran turquoise – Persian turquoise.
iridium – A hard white metallic element of the platinum group, the most corrosion-resistant and possibly the densest element known. In the massive form it is unaffected by all acids, including aqua regia. Melting point, about 2454°C.; specific gravity 22.4 to 22.6; chemical symbol Ir. Its main use is as a hardener for platinum, the alloys being used in jewelry, dentistry, electrical contacts, chemical equipment, pen points-, etc. The platinum alloy containing 10 per cent iridium, preferred for high-grade jewelry, is known as “hard platinum;” the 5 per cent alloy as “medium hard platinum.” See also PLATINUM GROUP.
iridosmine – (irr’i-doz”min) A naturally occurring alloy of osmium and iridium, also called iridosmium and osmiridium. The hard grains are used for tipping pen points and phonograph needles. See OSMIRIDIUM.
iris – Rock crystal containing thin cracks which show iridescent coloring. This type of material was formerly popular for gem use, and it is possible that some of the “opals” of the ancients were really this iris or rainbow quartz.
iris agate – A type of banded agate which, when cut into a thin slice and polished on both sides, shows an iridescent band when held up toward a strong light source. It is caused by refraction from innumerable microscopic crystals of quartz in certain layers in the agate; a coarser banding does not create the rainbow effect. As the agate must be sliced very thin, it has not found much gem use, most slices being mounted in cardboard so that the phenomenon may be observed at its best with the surrounding light shut off. Also known as RAINBOW AGATE.
iris diamond – According to Schlossmacher, a misnomer for a novel trick of coloring the lower facets of a diamond to give an imitation of strong dispersion and great fire.
Irish diamond – Misnomer for rock crystal.
Irish pearl – A natural fresh water pearl from the ancient fisheries at Omagh, Ireland.
iron core coil – An electromagnetic coil wound around a soft iron core.
iron glance – Hematite.
iron lap – A grinding lap made of malleable iron, used mostly with pulverized oilstone in oil as an abrasive for shaping and finishing steel parts of timepieces. Iron laps are made in forms of hand-slips for pivot and staff work, wheels for same purposes used on rotary pivot polishers, and flat benchlaps of large area for flat steel work.
iron opal – A weakly translucent brown, red, yellow or greenish variety of common opal. Also called JASPOPAL or OPAL JASPER.
iron oxide – Ferric oxide; iron rust; pulverized, washed and decanted, it is the rouge used for polishing jewelry, metal watch parts, etc.
iron pyrites – (py-rye’teez) A popular misuse and mispronunciation of the term pyrite. Though sanctioned by dictionaries, iron pyrites is never used by mineralogists.
ironstone china – A type of hard earthenware patented in 1813 by Charles Mason, supposedly having iron slag as one of its constituents. See STONE, CHIN A.
irradiation – A method of treatment to effect a change in a gemstone’s color involving the use of sub-atomic particles, x-rays, gamma rays, neutrons, deuterons or electrons. Successful in the more or less permanent coloration of diamond (brown, yellow, blue, green, black), beryl (green, golden), topaz (blue), tourmaline (pink, red, purple, yellow), quartz (smoky, amethyst). See RADIUM TREATMENT; PILE-TREATED STONES.
irregulars – A diamond shape classification, crystals of irregular shape with broken parts. Comes after “goods” and before “cleavage.”
isolator – (eye”so-lay’tor) Mechanism in a minute repeater for preventing contact of the click and the surprise piece until operation of the finger-slide on the case has been completed.
isometric system – (eye’so-met”ric) The preferred name of the cubic system of crystallization. Substances which crystallize in this system are isotropic and their crystallographic axes are all of equal length; hence the name, from “equal” and “measure.” See CUBIC SYSTEM.
isomorphous replacement – (eye’so-mor”-fuss) The replacement, chemically, of one element by another, without any disruptive change in most of the properties of the compound. Iron and magnesium, for example, replace each other isomorphously in the olivine series of minerals, and chromium probably replaces aluminum isomorphously in ruby.
isopropyl alcohol – A colorless inflammable liquid used by watchmakers for drying as well as dissolving shellac.
isotropic – (eye’so-trop”ic) Not birefringent, light passes through an isotropic substance in all directions at the same speed. Isometric minerals, glass and other amorphous substances are isotropic. See ANISOTROPIC.
Isobval – A whitish alloy used in hairsprings claimed to improve isochronal qualities.
Italian chrysolite – Vesuvianite.
ivory – The hard creamy white, opaque substance of which the tusks of elephants are composed, or, more generally, the teeth of any animal; walrus ivory, for example, is often used in decorative objects.
ivory clasp – A type of necklace cord end-fastener, consisting of two short barrels, attachable by a male and female screw, used for necklaces of beads other than metal beads.