jacinth – (ja-sinth) Reddish brown zircon, also known as hyacinth. Sometimes used, but confusingly, for grossular garnet of this color.
Jacobs chuck – An adjustable chuck with three jaws used in drill presses and adaptable for lathework.
Jacot lathe – A special-purpose watchmakers’ lathe, in which work is supported on dead centers and driven by a hand-bow, used for polishing watch pivots with hand-laps, to give them finish or to alter their form in adjusting See BOW LATHE; DEAD-CENTER LATHE.
jacut – Persian term for sapphire, and the root of our word, jacinth.
jade – A collective name which includes two minerals, nephrite and jadeite, of which the latter is the rarer and more valuable species. It is fundamental that the crystal structure be “felted”; i.e., not parallel but interlocking. Only then do we have a texture and toughness that makes jadeite and more especially nephrite, truly jade. Parallel fibred nephrite is known, cat’s-eye cabochons can be cut of it, but it cannot be regarded as jade when it has this structure, for it lacks the toughness of jade. Many other materials are carved by the Chinese, and many other materials are green and tough like jade, but none is properly called jade, other than these two. The colors have received various names in China as Hsi (white), Pi (blue), Lu (feather green), Kan (color of boiled chestnuts), Man (like veins filled with blood), Hsieh (black), Ch’a (fatty flesh), Juan (red and white). Buried jades are called Kan Huang (stained yellow), Lao Kan Huang (deeper yellow), Kzu Ch’ing (stained blue), Loa Kan Ch’ing (deeper blue), Hai Erh Mien (red with ashes), Chuen Ch’i Hsi (black from mercury), Tsao P’i Heng (date skin red with blood); imitation jade colors: Lao Ti Yu (chicken blood red, from an herb, a rare and ancient dye), Hsiu Ti Yu (colored by burning in a colored box); and ancient jades; Lao San Tai (soft excavated pieces). Names from Goette, “Jade Lore.” See NEPHRITE, JADEITE, CHLOROMELANITE, CHALCHIHUITL.
jadeite – (jade’ite) A sodium aluminum silicate containing some calcium magnesium silicate (a considerable amount in the case of the Mexican jade) and a member of the pyroxene group of minerals. The best comes from Upper Burma, where it is often found as boulders of hard, compact fibers; it is this structure which gives the jadeite its toughness, even though its hardness is not remarkable. Cavities with single, large transparent crystals are not known, the coarsest crystals seem to be those of the long-sought Mexican occurrence. Grayish, small, idiomorphic crystals have been found in California, but the occurrence has no economic value. Jadeite comes in many colors, of which white and whitish is the commonest; in all shades and tints of gray, orange-red, mauve, black, and green. The greens are the most valued and range up to a brilliant emerald hue, which, when uniform and fairly translucent, is very highly prized and goes under the name jewel jade. Its hardness is 6 to 7, its density about 3.3. See also AMPHIBOLE.
jadeolite – Misnomer for a deep green syenite resembling jade in appearance and coming from the Burma jadeite locality.
jager – (yah’ger) A diamond quality name, originally applied to certain fine diamonds coming from the Jagersfontein Mine, their slightly bluish color resulting from strong blue fluorescence; the highest grade in the traditional color scale.
jahalom – A stone in the breastplate of the High Priest of the Jews, long believed to have been diamond; now thought to have been corundum; derived from halom, “to beat” or “to overcome.”
jam-nut – A screw-nut used with another nut to tighten it after adjustment, as on a pendulum-bob regulator.
Japanese coral – Coral from Japan, the most common variety of which is dark red with a white core.
Japan pearl – An older, trade misnomer for the early cultured “half pearls” developed by Mikimoto before the spherical modern cultured pearls. See MABE.
jargoon or jargon – Name sometimes applied to white zircons offered as diamond substitutes. It has also been used for yellowish, off-color diamonds.
jaseron chain – A fine gold chain worn in the 19th Century, with crosses, pendants and mosaics.
jasper – 1. A fine-grained, impure, massive quartz aggregate, characterized by a lack of any regularity of orientation of the microscopic quartz crystals and by its complete opacity. It has a smooth, conchoidal to uneven and angular fracture and a dull to greasy luster on the fracture face. Usually it is strongly colored. The differentiation from agate and chalcedony by cutters is based upon the transmission of light — when the stone is completely opaque, even on thin edges they call it jasper; if translucent, even slightly, it is called chalcedony; and if translucent and brightly colored, agate. See also ADINOL; BANDED JASPER; BLOODSTONE; BLOOD JASPER; BOAKITE; BIRD’S EYE; QUARTZ; CATALINITE; CHERT; CREOLITE; HELIOTROPE, etc. 2. Stoneware. A hard, dense stoneware developed in 1775 by Josiah Wedgwood; body colors, often with the well-known white relief, included black, yellow, green, blue and lilac.
jasperine – Banded jasper of varying colors.
jasper jade – Misnomer for green jasper.
jasper lap – A polishing lap used in watchwork, made of natural stone of opaque impure silica, usually red in color. Jasper laps are made of flat form and considerable area, for polishing jewel settings by hand-rubbing; or in the form of long thin slips mounted in handles for polishing pivots on a lathe.
jaspilite – (jass’pi-lite) Banded hematite and jasper.
jaspis – Ancient name for chalcedony.
jasponyx – (jass’po-nix) An opaque material with the banding of an agate, but grading into a jasper.
jasp opal – Intermediate stage between jasper and opal.
jet – A black, compact variety of the brown coal, lignite, which takes a fine, velvety polish. It is soft 3-4 on the Mohs scale and light in weight (1.30-1.35 s.g.); like any other coal, it will burn. Popular in the middle of the last century, it is little used today, its place being taken by harder stones, like onyx and black tourmaline. Chief source, Whitby, England.
Jet Black – A commercial solution which coats gold with a black coating. May be applied by heat or by electroplating.
jet glass – A black glass made to imitate jet. Harder than true jet, it will not burn and is not marked by a hot needle.
jet stone – Black tourmaline, though it is rarely used, as other substitutes are cheaper.
jewel – 1. A stone or other substance, as pearl or amber, cut, polished or otherwise prepared for use or beauty. 2. An ornament, usually for personal wear, made of precious metal or an imitation of precious metal and often set with gems. 3. A bearing for a pivot in a watch or other precision instrument, formed of corundum, garnet, glass, etc.
jewel bezel cutters – Sets of steel bits used in lathe chuck or hand-drill for forming seat and bezel for setting watch jewels directly into place or bridge.
jeweler – 1. A merchant who sells diamonds, other gemstones and jewelry, as well usually as watches and clocks and, often, silverware, china, crystal, giftwares and other merchandise. 2. One who makes or repairs jewelry, as distinguished from such other craftsmen as watchmakers or engravers.
Jewelers Board of Trade – A credit-rating and collection agency of Providence, R.I., founded in 1874; supported by 1300 manufacturers, wholesalers and importers; publishes a semiannual Confidential Reference Book and a weekly service bulletin.
Jewelers Security Alliance of the United States – A non-profit crime-prevention association of retail, wholesale and manufacturing jewelers; founded in 1883; pays reward for arrest and conviction of individuals committing crimes against members; helps members in crime-prevention.
Jewelers Vigilance Committee – Sometimes defined as “the conscience of the industry;” incorporated in 1917 “to investigate complaints of violations of stamping, misbranding, false advertising and similar laws … To keep in touch with members of the jewelry trade in all parts of the United States, with a view to cooperate with such members and other bodies, in the enactment of needed legislation … to the end that in time such laws shall be uniform and efficacious in all parts of our country.”
jewelers’ lathe – A lathe for polishing work with rotary buffs, comprising a spindle and pulley in bearings on a simple bench mounting, differentiated from the watchmakers’ lathe or other lathes used for turning. See LATHE.
jeweling caliper rest – An attachment for an American-type watchmakers’ lathe, for automatically measuring diameters of jewels to be set, and mechanically transferring the measurement while cutting seat for jewel in a blank for setting.
jeweling chuck – Special split wire chuck for holding jewel settings during recessing, burnishing, or stripping operations; one form is an assortment of split chucks small enough to hold in a large size lathe chuck; another is an assortment of regular lathe chucks with recesses countersunk on face around hole, of various diameters to hold jewel settings.
jewel hole gauge – A tapered steel pin, mounted to slide in a handle with graduated scale, with an index on the pin that indicates on a scale the diameter of hole in a watch jewel.
jewel pin – See ROLLER JEWEL.
jewel-pin setter – A device for holding and applying heat to the roller table of a lever escapement, to soften cement while replacing or resetting a roller jewel.
jewel pusher – Set of punches of assorted sizes, made of soft metal, for removing jewels from watch plates and bridges.
jewelry – Articles of personal adornment such as rings, bracelets and necklaces, made of precious or non-precious materials, often set with natural, synthetic or imitation stones or natural, cultured or imitation pearls.
jewel-screw countersinks – Sets of small flat-bottom recessing mills with centering pins, for cutting sinks intersecting a watch plate and jewel setting, to hold screws fastening setting to plate.
jewel setting – 1. A metal ring in which a hole or cap jewel is set by burnishing the corner of the jewel seat over the edge of jewel, the outer edge of the setting then being turned to fit a recess in a plate, bridge or cock of a watch or clock. 2. The operation of setting jewels. See JEWELING.
jewel tweezer – A tweezer with a device for locking its jaws in place to hold watch jewels without slipping; with recesses in the jaw tips, used while cleaning gems to avoid risk of losing them.
jigger – A bar accessory measuring cup, usually of 2 oz. capacity; when made as two cups, base to base, the second cup has 1-oz. capacity.
jobber – A term now generally regarded as archaic and in disrepute for wholesaler.
jobbing stones – A jeweler’s assortment of unmounted stones, kept for use in repair work.
job shop – Term used in the watch and jewelry trade to designate a “trade shop” that does repairing, as distinct from a shop where goods are manufactured.
Job’s tears – Small pebbles of chrysolite or peridot, from Arizona and New Mexico.
johnite – Vitreous or scaly turquoise occurring in siliceous schists, named after J. F. John who (in 1806) had furnished the best analysis of that mineral to date. See also TURQUOISE; AGAPHITE; CALLAITE.
joint – 1. An item of jewelry findings, soldered or screwed to a piece of jewelry, to form, with a pin, a hinge for the pin with which the piece is fastened to clothing of wearer. 2. A hinge formed by three or more sections of tubing. See JOINT WIRE.
joint buff – A hard felt buff of lenticular form, for use on a jeweler’s lathe, for polishing in crevices or grooves.
jointer – A hand-driven milling tool, for cutting parallel sides on a joint to prepare for soldering in resizing or repairing finger rings.
joint file – A file with flat parallel uncut sides and rounded edges cut with teeth, to produce grooves into which the joints or knuckles of a hinge are soldered, for watch cases, lockets, etc.
joint fork – A large fork with two long tines, used to hold a roast of meat in position while carving.
joint pin – The metal pin fitted friction-tight in holes in end-joints of hinges of watchcases, etc., on which the lid-joint of a case, or a pin-base turns as a bearing.
joint pin pusher – Steel punch, used in sets of assorted sizes, for removing hinge pins of watch cases and jewelry.
joint tool – A device for cutting tubing and filing the ends square. The tubing, placed in the triangular opening and held in position by its set-screw, is cut or filed against the hardened surface of the tool.
joint wire – Hollow wire or tubing formed by bending a strip of thin, flat plate and drawing it through a drawplate until the desired diameter and opening are obtained In making seamless tubing, a disc of metal of appropriate thickness is successively punched to cup shape and drawn to desired size. Used to make hinges for watch cases, lockets, etc.
Jolly balance – An instrument used for the determination of specific gravities of minerals. It consists of a slender spiral spring suspended from a standard on which a scale is marked and supporting a pan or pair of pans with which the weights of the stone in question can be determined for both air and water. It is named for its inventor, P. von Jolly, a German physicist.
journeyman – A workman who has completed learning his trade, and is fit to hold a job as a full-fledged workman, as a journeyman watchmaker or jeweler; to differentiate from an apprentice, student, or other workman who cannot do all the work.
jubilee cut – A modified brilliant cut named in commemoration of the sixtieth anniversary of Queen Victoria’s accession in 1897. In it the table and culet are replaced by extended star facets and other modifications are made in the other facets, making a total of 88 facets.
jug – A deep plain vessel of china or silver for holding liquids. It usually has a handle, flat base, circular body and small lip.
jump-figure dial – A timepiece dial mechanism in which the numerals are on disks, moved usually each minute by a pawl and ratchet, and appearing in a small opening in the dial-plate to indicate time. Some timepieces have hours only shown in this way; others, hours and minutes. See RATCHET.
jump ring – An item of jewelry findings; plain rings of graded sizes and various metals, round or oval, the ends of wire meeting but not soldered together, for attaching parts of jewelry together, in manufacturing assembling, or repairing.
K, Kt – Abbreviations for karat.
kahurangi – A pale-green translucent variety of New Zealand nephrite jade.
Kalmuck agate, opal – See CACHOLONG. The name is probably derived from an occurrence on the Cach river, in Bokhara, central Asia.
Kandy spinel – False name under which Ceylonese almandite garnet is sometimes sold.
kaolin – A fine white clay consisting of decomposed feldspar, a non-fusible silicate of aluminum; a component of porcelain. Also called china clay.
kaolite – Name given in Arizona to molded stones of various colors, made in imitation of Indian carvings, cameos, etc., for use in costume jewelry. Presumably a baked clay, the name is from that of the principal clay mineral, kaolin.
karat – One twenty-fourth part by weight of the metallic element gold in an alloy. Pure or fine gold is 24 karats; 18 karat gold (abbreviated 18 K. or 18 Kt.) consists of 18 parts of pure gold, mixed with 6 parts of other metal; 14 karat gold (abbreviated 14 K. or 14 Kt.) is 14 parts of pure gold, combined with 10 parts of other metal; etc. Together with carat, which see, the word is probably derived from the Greek, kemtion, signifying a seed used in ancient times for weighing pearls. Its connotation of l/24th, as applied to gold, stems from the weight of the solidus, a gold coin used in Byzantium from 312 A.D. to 1453 A.D. By law, the solidus weighed 4 scruples, each of which was equal to 6 kerations; thus, the solidus weighed 24 kerations or karats. In England, the spellings “caract” and “carrott” were used as late as the 17th Century, superseded by “carat,” which is still used outside the United States with the same spelling to denote both the ratio of fine gold in an alloy and the unit of weight for gemstones. In U.S. usage karat designates the proportion of fine gold in an alloy; while carat is applied to the weight of a stone. See CAROB; CARAT; TOLERANCE.
Karat Clad – A registered trade name for heavy gold electroplate, meeting Federal Trade Commission regulations for gold coating at least 100 microinches thick. See HEAVY GOLD ELECTROPLATE.
karat gold – A gold alloy of not less than 10 karat fineness, preceded by the karat fineness of the alloy, such as 14 karat gold or 14 K. gold. Fineness may also be designated without the word gold, such as 14 Karat or 14 K.—From Rule 22, U.S. Federal Trade Commission Rules for the Jewelry Industry. The International Confederation of Jewelry, Silverware, Diamonds, Pearls and Stones (CIBJO) favors two standards of gold for international commerce: 18K and 14K. See TOLERANCE; PLUMB GOLD; NATIONAL STAMPING ACT.
karat needles – A set of brass tongues hinged on a handle, tipped with various karat-grades of gold, used with test stone and acid to determine the fineness of a gold object. See TOUCH-
STONE; ACID TEST.
karfunkel – The ancient indefinite name of Indian legends for a red stone; in the Middle Ages “karfunkel stones” were principally garnets.
Karlsbad Spring stone – A banded red, white and brown gypsum used in small carved objects and cheap jewelry.
karrusel – (kar’oo-zell”) Arrangement of the connection of train with escapement in a watch, in which the entire escapement and balance is in a framework pivoted so that it keeps turning to all the vertical positions as the watch runs, more or less eliminating position errors of time-keeping. This is a variety of “tour-billon” construction, invented by B. Bonniksen, of Coventry, England, in 1902. See TOURBILLON.
Kashan synthetic ruby – Synthetic, flux-fusion ruby made in Dallas, Tex., by Dr. Trueheart Brown.
Kashmir sapphire – Theoretically, cornflower blue sapphires from the Zanskar range of the northwestern Himalayas in Kashmir, but, as generally used in the trade, the name for any sapphire of this fine quality. They are characterized by a slight velvety look (cloudiness) and fine blue hue in all lights and are considered the ultimate in sapphires.
kawakawa – Maori name for the ordinary green variety of nephrite jade. See PUN AMU; INANGA; KAHURANGI.
kawk – Cornish synonym for fluorite.
keeper – Band around wrist watch strap near buckle, to hold end of strap in place.
keeper ring – Originally, “Bride’s ring.” A diamond hoop worn above the wedding ring. In modern times, a guard ring.
kerf – The groove in a diamond, cut in preparation for the cleaving.
Kew certificate – A certificate stating results of tests of timekeeping of a watch or chronometer, issued by National Physical Laboratory at Teddington, England. Prior to 1900 the tests were made at Kew Observatory, Richmond, England, and the prestige there established for Kew certificates was so high that the name was retained when the testing was moved to Teddington. The certificates for passing tests, with highest requirements are designated Class A; and for a less exacting series of tests, Class B.
keyhole plate – In weight clocks, the brass disc with an eccentric hole intersecting the concentric hole of less diameter that slips into a groove on the mainwheel arbor, to hold the mainwheel against the barrel, and permit movement of barrel during winding.
keyless – Horology. Term used elsewhere than in America to describe watches wound and set by a button (crown) on end of the stem, outside the case.
key-pattern – See GREEK KEY PATTERN.
key-regulator – A type of regulator, used mostly in Swiss watches with flat hairsprings, in which the spring-terminal is in a space between ordinary curb-pin, and a metal block called the key, boot, or gate-block, at the lower end of which is a finger that may be turned to extend across the opening to touch the curb-pin, to prevent the spring coil from jumping out if the watch receives a shock as when dropped, etc. See CURB-PINS; REGULATOR.
key ring – An adjustable device to hold keys. In simple form these are made as split rings onto which keys are introduced by forcing the split sections apart. More elaborately, they are made of spring-loaded holders and threaded devices, in gold and silver.
keystone – A system of quoting wholesale prices of jewelers’ goods. It means that 50 per cent of the price stated in a catalog or price list shall be understood as the wholesale price. Originated in 1896 by Keystone magazine, a predecessor of Jewelers Circular-Keystone, after subscribers had complained against the showing of dealer costs in a publication that customers might see on jewelers’ counters.
keystone cut – A fancy diamond cut, whose outline is that of a keystone.
key-stud – In an American-type watchmaker’s lathe, the short pin in the spindle throat that engages the slot on shank of chuck to prevent its rotation in relation to the spindle.
keywinder – Watch wound and set with a separate key, differentiated from a stemwinder (American) or keyless (English) watch.
Killicranke diamond – White topaz from Tasmania.
kilo – In the metric system, one thousand, as in kilocycle, kilogram, kilometer, kilowatt, etc.
kilogram – One thousand grams, five thousand carats, or 2.2046 pounds.
kimberlite – Mottled greenish to bluish-grey or black rock filling the throats of ancient volcanoes, a small proportion of which contain diamonds. It was named for Kimberley, South Africa, where the first identification of such rock had just been made. Similar diamond-bearing volcanic pipes or fissures have been found elsewhere in Africa as well as India, Siberia and North America.
kinetics – The laws governing the energy possessed by a moving body due to its motion.
king cut – An additionally faceted brilliant cut, with 49 crown facets and 37 pavilion facets instead of the customary 33 and 25.
king topaz – An erroneous name for yellow to orange sapphire.
kinradite – A local trade name for iron-oxide-stained yellow, red and brown spherulitic jasper from California.
kite cut – A fancy diamond shape, resembling a boy’s kite in outline.
klaprothine – Lazulite.
knee punch – Staking punch of a form to permit entering the shell of a cylinder, for driving out pivot plugs. See CYLINDER ESCAPEMENT.
knife edge – 1. An item of jewelry findings, wire of gold, etc., drawn so that a cross-section resembles that of a knife blade or wedge. 2. A fulcrum for pendulum suspensions, or for beam of precision weighing scales, affording sensitive movement.
knife edge file – A form of file for cutting work in an acute angle, with double-cut teeth on sides and single-cut teeth on edges.
knife-edge girdle – A thin, easily-chipped girdle of a gemstone; American Gem Society regards 0.175 mm. as the minimum desirable thickness for the girdle of a brilliant cut diamond.
knuckle – One of the tubular sections that form the hinge on the lid of a watch case, locket, etc., in connection with the hinge-pin.
knurling – A milled or corrugated surface produced on the circumference of a key or adjusting nut, to enable a firm hold with fingers in winding or tightening; produced by pressing a notched steel roller, a “knurl”, into the blank while rotating in lathe.
Koloriscop – A light box for the color-grading of diamonds, patented by Dr. E. Giibelin of Switzerland.
Korea jade – Misleading name for serpentine.
kornerupine – (kor’new-roop-peen”) A rare and unusual gem, a magnesium aluminum silicate, usually yellow or brown, but found in Madagascar in gemmy sea-green crystals in a pegmatite. It is about 6l/2 in hardness; the gravity is 3.28 to 3.34, the refractive index L669 to 1.682. It crystallizes in the ortho-rhombic system and has a strong pleochroism, green to yellow to reddish brown. It is of interest only to collectors of unusual gems.
kouphotite – Prehnite.
krantzite – One of the amber minerals, of no gem importance.
kunzite – One of the gem varieties of the mineral spodumene. Kunzite was first found in the tourmaline mines of Pala, Calif., and was named for George F.Kunz. It is lilac in color, strongly pleochroic, the refractive index range is 1.660 to 1.675 and the specific gravity about 3.19. See SPODUMENE.
kyanite – (ky’an-ite) A common mineral, an aluminum silicate used in the manufacture of heat-resistant ceramics, which is sometimes found in flat elongated gemmy bluish crystals. The refractive indices are 1.712 to 1.728, the specific gravity about 3.67, and the hardness most interesting. It is an outstanding example of the difference in hardness in crystal directions, a phenomenon usually too small to be observable by simple methods. Parallel to the elongation of the crystal, the mineral can be scratched by a knife; its hardness is about 4 to 5, while across the crystal its hardness is about 7, and a knife leaves no mark.
L – Abbreviation for “let-off;” denoting the pallet (L-stone) in lever escapement, whereon escape-wheel teeth act last, in their passage through the escapement. See LET-OFF; R.
Labrador feldspar, Labrador moonstone – Labradorite.
labradorescence – (lab’ra-dor-ess”sense) The vivid coloration displayed by a properly oriented section of labradorite. See ADULARESCENCE.
labradorite – (lab’ra-dor’ite) A gray plagioclase feldspar in which the proportion of soda to lime is about 2 to 3. It is notable for the spectacularly colored reflections visible on a properly oriented face viewed and illuminated at the correct angle. According to Robert Webster, the optical effect that makes these colors is “mostly due to interference of light from the fine lamellae of the repeated twinning” and to platelets and needle-like inclusions of magnetite. A deep blue or green, like a Brazilian butterfly’s wing, is the most common effect, but this may shade to green, yellow, bronze or red. Transparent labradorite had been found in volcanic rocks in Utah, Oregon and New Mexico. Faceted stones of this material are interesting to collectors. At Plush, Ore., there are crystal portions that show red and green, and cut stones remind experts of andalusite. See BULL’S EYE; CHANGEANT.
Lake George diamonds – A fanciful misnomer for the brilliant, doubly terminated colorless quartz crystals for which New York’s Herkimer County is famous.
Lake Superior greenstone – Chlorastrolite.
lambrequin – A cartouche on some clock dials in the form of a curtain-drape bearing the maker’s name.
lambreu – Brazilian term for brilliant irregular fragmented diamonds.
laminated balance – Term sometimes used denoting a compensating balance. See BALANCE.
landerite – A name which has been given to the pink grossularite in white marble which comes from Xalostoc, Morelos, Mexico. See ROSOLITE
landscape agate – A variety of moss agate which gives the effect of a scene, as opposed to other types resembling figures, trees, etc.
lanisher – A belt sander used to smooth flat areas prior to polishing.
lap – 1. A horizontal spinning wheel about one foot or 18 inches in diameter against which gems are polished. Diamond laps are composed of soft iron, which best retains the diamond dust doing the actual cutting, and they rotate at high speeds, 2000 to 2400 revolutions per minute. Softer gems are cut on similar laps of varying metals, and at lower speeds. 2. Horology. See LAPPING. 3. Jewelry making. A horizontal or vertical wheel 6″ to 8″ in diameter, charged with fine abrasive, against which jewelry is polished to obtain flat, smooth surfaces. Jewelry laps are made of felt, wood and metal. See LAPPING; SPLIT LAP.
La Paz pearls – The common trade name under which the often bronze-colored pearls of the hammer-head clam, Malleus, are sold. They are found in the Gulf of California, and the waters adjoining Guatemala, Panama and Venezuela, and are also sold as Panama or Venezuela pearls.
lapidary – (lap’i-dare-ee) A person who cuts and polishes gems except, in trade usage, diamonds. In older usage, a treatise on gems was called a lapidary.
lapis-lazuli – (lay’pis-laz”you-lie) Usually a mixture of lazurite with one or more associated minerals, calcite and pyrite. It is an attractive blue stone commonly used in decorative carvings and for beads and cabochon gems. The best quality material is found in Afghanistan; other localities are Siberia, Chile and California. See LAZULITE.
lapped border – An article is said to have a lapped or rolled edge when the metal has been rolled over the edge and spun under to give the effect of a rounded edge.
lapper – A specialist in one phase of diamond finishing, the man who puts the 18 fundamental facets on the stone. They are the four top corner, the four bezel and the table facets on the crown, and the four bottom corner, the four pavilion and culet facets in the pavilion. The stones are then finished by the brillianteer, who puts the additional 40 facets on the stone. 2. Jewelry making. A jewelry polisher specializing in lapping, the polishing of flat surfaces such as are produced on watchcases and other articles calling for precise, flat surfaces. See LAP; SPLIT LAP.
lapping – 1. Diamond polishing. The process of cutting the first eight top, the first eight bottom, the table and the culet facets on a brilliant cut diamond. See BLOCKING. 2. Horology. Abrasive process for shaping and finishing hardened steel parts of timepieces. Laps are of two main forms: a flat slab of soft metal, on which an abrasive is spread and the work rubbed on it, to reproduce the flat surface of lap on the work; or a disc or wheel rotating on a spindle and held in contact with the work. Coarse abrasive is used on laps for shaping work, and finer abrasives for polishing. In the soft metal of the laps the grains of abrasive imbed themselves under pressure of the work, so that their sharp corners are held to cut the hard metal of the parts being lapped, thus reproducing on the work the form of a lap. See ABRASIVE. 3. Jewelry. The art of producing flat, smooth surfaces on jewelry by means of laps. See ABRASIVES.
laser – Term under which an optical maser has become known; an acronym for Light Amplification by Stimulated Emission of Radiation. Using a fluorescent gas or doped solid, such as a synthetic ruby crystal, it produces a powerful, intensely hot, straight-line beam of light of very restricted diameter, capable of burning its way through solid substances.
laser drilling – A method, developed in late 1960’s, for improving the appearance of a flawed diamond by boring a laser-beam hole into the inclusion. Merely piercing the inclusion may cause it to turn white; other inclusions must be leached out by acid or other volatile liquid. Drill holes, sometimes only 0.5/1000 of an inch in diameter, may be scarcely visible under 10X; they often appear as a “V”, due to reflections from the entering-facet surface.
Laser gem – Promotional name for a doublet imitating a diamond.
lasque – A thin tabular diamond crystal; such material has been used in the past to glaze miniature paintings; also called portrait stone.
latch – The device used on index-plate of a watchmaker’s wheel-cutter to hold the work stationary during the milling of each tooth-space.
lathe – A machine for rotating work to be shaped by turning, milling, polishing, grinding, drilling, etc. In the watch and jewelry trades, the principal forms of lathes used are the watchmaker’s lathe for shaping and finishing parts for timepieces, and the jeweler’s polishing lathe for finishing work with buffs and abrasives. Modem jewelry lathes are precision, high-speed instruments used to turn wedding bands to size and shape and to effect diamond finishes inside and outside of the ring. See ATTACHMENTS.
lathe-loupe – A watchmaker’s magnifying glass made to attach to lathe instead of worn over the workman’s eye.
lathe mandrels – Metal tapers of graded diameters or of split expansion type, for holding rings or the like during turning operations in a lathe.
lattice – Term used for the atomic arrangement within a crystal which is responsible for the external shape and the directional optical and physical properties of a crystallized substance; thirty-two variations are possible.
lava – (lah’va) Molten rock flowing from a volcanic vent, and the rapidly solidified product of that activity. It sometimes contains crystals of gem materials, such as chrysolite; a compact bluish glassy variety from Vesuvius has been cut into cameos and intaglios. See OBSIDIAN.
lavaliere – (la-vahl-yare) An article of jewelry consisting of a pendant suspended on a chain or light necklace; after the Duchesse de La Valliere (1644-1710), a mistress of Louis XIV.
lax diamond – Term for a dull, fireless diamond.
lazulite – (laz’you-lite) Not to be confused with lazurite. Lazulite is a blue monoclinic phosphate of iron, magnesium and aluminum, a little heavier but of about the same hardness as the other mineral. Its blueness is not as intense as that of the best lapis lazuli, and it is not associated with pyrite. Usually it is of no gem significance in the trade, but discoveries in Death Valley indicate a potential supply of attractive decorative material. Other localities are Brazil, where it has been found in deep blue transparent pebbles and masses, Georgia and Austria. Brazilian diamond specimens showing a matrix of lazulite are probably faked. Available, very rarely, in faceted deep blue, strongly pleochroic gemstones, with a r.i. of about 1.63, hardness of 5%, and a density of 3.17.
lazurite – (laz’your-ite) The principal, to exclusive, mineral ingredient of lapis lazuli. Lazurite is a deep blue sulphur-bearing sodium aluminum silicate, the color of which is caused by the sulphur present. Two related minerals may partially replace lazurite without destroying the molecular structure, and consequently, the dodecahedral crystal habit. Its hardness is about 5%, the specific gravity about 2.4 (lapis lazuli containing pyrite, over 2.7) and the refractive index 1.50. See LAPIS LAZULI.
lazurquartz – Sapphire quartz.
lazurspar – Lapis lazuli.
leaching – 1. A technique, introduced about 1940, for improving the appearance of some flawed diamonds; hydrofluoric acid is used to reach inclusions open to the surface or from which fractures or cleavages radiate to the surface; thus unsightly flaws may be “leached” white. No means of detection is known. 2. Acid or other secret liquid used, since the end of the 1960’s, to leach out certain inclusions that have been reached by laser beam. See LASER DRILLING.
lead – A heavy, pliable, inelastic metal, having a bright, bluish color, but easily tarnished.
lead glass – Imitation gemstones. A high-index glass containing a considerable proportion of lead oxide. Its refractive index and hardness vary with the lead content. Flint glass is a frequently used formula of a lead glass; the refractive index is about 1.62 and the specific gravity about 3.4.
lead screw – A turning machine screw in a mechanism which advances or retracts a device attached to it.
leaves – Horology. The cogs on a pinion in gearing, differentiated from cogs on a gear wheel, which are called teeth. See GEARING.
lechoso opal – (lay-cho’so) A name of no particular significance, but about which there seems to be some difference of opinion. Lechoso probably is derived from a Spanish word for milk, and so should mean a milky, almost clear opal of the Mexican type. Schloss-macher, however, attributes this name to the Mexican fire opal which shows some of the color flashes of precious opal in the red ground color. Others restrict the term to opal showing green to violet color flashes in a colorless mass.
L.E.D. – See LIGHT EMITTING DIODE.
left-hand screw – A screw with thread made to turn counter-clockwise, contrary to most screws in this respect; used in some watches to hold parts in the stem-winding and setting mechanism the motion of which would tend to unscrew a right-hand threaded screw.
left-handed fuzee – A fuzee movement in which, dial down, the third wheel is at the left and the balance is on the right.
lemel – Miscellaneous sweepings from jewelry shops, including filings, chips from engraving, bits of solder, etc., too small to be treated by known kind and quality of metal. Lemel is “sweep-smelted” and refined to reduce and separate what is in the mixture, for recovering the value of the metals. See SCRAP.
lentil cut – A cabochon cutting in which both sides have the same convexity, usually a rather flat thin cabochon stone, of the type of many opals.
lentille – Form of watch crystal for open-face cases, in which the edges inside the bezel are rounded off; made originally like mi-concave glasses with a sharp-cornered beveled edge, the polishing off and rounding of this corner is what produces a lentille crystal. See WATCH CRYSTAL.
lepidolite – (leh-pid’oh-lite) A lithia mica commonly found in pegmatite dikes and an associate of colored tourmalines, etc. Often attractively colored in shades of lavender, compact masses have sometimes been used in decorative carvings, though its mica softness is conducive to neither a high polish nor durability.
Lepine calibre – A movement first designed by Jean Lepine (1720-1814), in which each wheel has its own “bar” or bridge.
let-down plier – A plier devised for releasing the tension of a clock mainspring preparatory to disassembling the clock.
let-off – In the action of a lever escapement, the cessation of contact between an escape-wheel tooth and a pallet; the corner of pallet where this occurs is called the let-off or “L” corner. This term also distinguishes the one of the pair of pallet stones where all teeth of the escape-wheel in turn are let off or discharged from action in the pallets; hence called the “L” or let-off pallet stone, differentiating it from the receiving or “R” pallet stone, at which all escape-wheel teeth are received into action with the pair of pallets.
leuco sapphire – (lue’ko) Colorless sapphire.
leveler – A tool with a small slot on the end of a steel wire, at a right-angle to the length of the wire, used for making slight bends on hairspring coils, to bring them all into the same plane when truing a hairspring.
lever – Horology. In the pallet-fork-and-arbor assembly of lever escapement, the lever is the steel bar between the fork and the pallet.
lever escapement – The escapement long established as best for use in watches; invented by Thomas Mudge, London, England, about 1765, a detached type escapement, with pallet-fork-and-arbor assembly between the escape-wheel and the balance. See DETACHED ESCAPEMENT; ESCAPEMENT.
lever-fork polisher – A tool comprising two flexible laps, for polishing the inside acting surfaces of a fork-slot of a lever escapement.
Leveridge gauge – An instrument which permits a weight estimate from the dimensions of a cut stone; invented by Athos D. Leveridge in 1937.
lever-set – Type of hand-setting mechanism for watches, in which a lever is pulled out from side of dial, to shift the mechanism from winding to setting condition. This type of setting is favored by railroad watch inspection rules, because with it, it is impossible to leave watch in setting position accidentally, which could cause an error in timekeeping. See PENDANT-SET.
LI – Abbreviation for “lightly included.” See CLARITY GRADE.
lift – The phase of wheel-and-pallet action in a lever escapement that takes place while an escape-wheel tooth is passing over the lifting face of a pallet stone. See IMPULSE.
lifting-piece – In a striking clock mechanism, the lever that lifts the rack-hook, preparatory to striking.
lifting spring – In a hunting watch case, a spring that lifts the lid over the dial, when the locking spring is released.
ligament pearl – A pearl which formed near the hinge in the ligaments. Such pearls are usually elongated distorted masses of no particular value.
light brown – A commercial color classification of diamonds; according to Eric Bruton, between fine light brown and dark brown and equivalent to cape in the white-to-yellow series.
light cape – A commercial color classification of diamonds; according to Eric Bruton, between silver cape and cape.
light-emitting diode – A tiny dot or bar of a chemical-metallic element that glows when stimulated electrically, used in digital displays of some solid state timepieces. There are a number of diodes for each digit and from them any numeral from 0 to 9 can be arranged. Because light-emitting diodes require current in the milliamp range, and because a tiny battery can supply only about 100 milliamp hours per year, there cannot be a continuous time display. Therefore, watches with light-emitting diodes show time only upon command, as upon the pressure of a button.
light opal – White Cliffs opal.
light platinum metals – Ruthenium, rhodium, and palladium, metals of the platinum group, but of considerably lower specific gravity than platinum.
lights – Term used by chronometer makers to denote the spaces between the edge of an impulse roller and the points of the nearest two escape-wheel teeth when the escape wheel is at rest between unlockings. In adjusting the chronometer escapement, these lights or spaces should be made equal.
light yellow – A color classification in the Scan, D.N. system equivalent to 0, P, Q and a portion of R in the GIA system or to 8 and a portion of 9 in the American Gem Society system.
ligne – (leen’y; line) An ancient French unit of measurement, still used for designating the diameters of watches, especially watches of European origin. A ligne is the equivalent of 2.255883 millimeters, or .08883 inch. See WATCH SIZES.
lilalith – Lepidolite.
lime – Calcium magnesium oxide, sometimes used in place of crocus as a polishing agent.
lime, Vienna – A compound of oxide of calcium and magnesium, obtained by exposing slaked lime to air, formerly used extensively by American factories for polishing steel.
limonite – (lie’monite) A brown hydrous oxide of iron of indefinite composition. It is a common ore of iron and is often found as a thin coating over gem minerals, imparting a yellow tinge. Commonly associated with turquoise, it is often the brown matrix material so frequently cut with that gem.
Linde Star – Synthetic star rubies and sapphires produced, 1947-1975, by the Linde division of Union Carbide Corp.; marked with an L on the back, to distinguish them from those made by other manufacturers.
liner – A graver used for engraving a series of parallel lines close together, with a single cut of the tool.
line finish – A finish used on parts of timepieces, consisting of a series of fine parallel lines, scratched on the metal surfaces by rubbing the part, with motions strictly in one direction and reverse, on a flat surface charged with an abrasive; or by rubbing an abrasive lap similarly on the work. See POLISHING.
line-of-centers – An imaginary line passing through the centers of wheels and pinions.
lintonite – (lin’ton-ite) A name for the mineral related to thomsonite which is found in green and pink banded pebbles on the shores of Lake Superior and often cut and used locally for a gemstone.
lips – Horology. The edges of the half-shell portion of cylinder in a cylinder escapement, which act as pallets while being given lift by the inclines on the escape wheel teeth. See CYLINDER ESCAPEMENT.
liquid crystal – A type of display used in some solid state timepieces in which time is shown by means of a sophisticated liquid sealed wafer-thin between two slender glass plates. Sealed in with this liquid, but glued to the inner surface of one of the plates, is a set of current-carrying but transparent segments of numbers, connected by tiny wires to the circuit. When selected segments are stimulated electrically, the liquid in front of these segments changes from clear transparency to opacity, or becomes light-reflective, to form numerals denoting the time. Because the liquid crystal display needs current only in the millionths of an ampere, liquid crystal displays can remain on constantly. See DYNAMIC SCATTERING; FIELD EFFECT.
liquid inclusion – An inclusion within a crystal that is filled with a liquid, usually recognizable as such only if there is also a gas bubble present, which can move about, or some solid material that can be seen to slowly tumble down as the specimen is turned.
Lisbon cut – A modification of the brilliant cut, giving the stone 74 facets.
lithion beryl – Name given to a lithium-containing and caesium-free variety of beryl, from Schlossmacher’s analyses. It would seem to be generally an aquamarine.
lithia mica – Lepidolite.
lithia lazuli – Violet fluorite.
lithoxyle – (li-thoks’ill) Opalized wood in which is preserved the grain of the original material.
litoslazuli – A misleading term which has been applied to the purple massive fluorite from Sierra de Cordoba, Argentina, in reference to a fancied resemblance to lapis lazuli.
liver opal – Menilite.
live-spindle lathe – A watchmaker’s lathe of the American type, in which the work-holding spindle rotates with the work; differentiated from the dead-center or European type lathe, in which the spindles are stationary with the work rotating on their centers. See DEAD-CENTER LATHE.
loam – An ocreous earth prepared for painting on soldered joints in jewelry work, to protect a joint from heat while additional soldering work is being done. See OCHRE; YELLOW OCHRE.
lock – Horology. The condition in action of a lever escapement during which the motion of escape wheel is stopped by contact of one of its teeth with the locking-face of a pallet stone. See UNLOCKING.
locket – A piece of jewelry worn suspended on a neck chain, comprising two lids hinged together, for containing a portrait, lock of hair or other personal souvenir.
locking jewel – In a chronometer escapement, the upright flat-faced pin of ruby or sapphire, set in the detent, against which an escape wheel tooth rests during locking of the escapement.
locking, equidistant – Lever escapement design which has the locking corners of each pallet jewel equidistant from the pallet (arbor) center.
locking spring – In a hunter-type watch case, the spring that presses the catch into its seat upon release of the crown in closing the case; the catch engages the lid of case to hold it closed.
lodestone – Magnetic magnetite. Magnetite is a black oxide of iron which is attracted by a magnet and which is an important ore of iron. Some specimens of magnetite are themselves magnets, they are then known as lodestones and are often sold to the gullible as good luck charms.
long case clock – The proper term for a tall clock standing on the floor, otherwise known as floor clock, hall clock, grandfather clock.
long-nose plier – A form of plier much used in clock repair work, with jaws of extra length for reaching between plates.
loops – Items of jewelry findings, for suspending lockets, etc., to necklace chains; usually soldered to the locket.
lorgnette – (lorr-nyett’) Eyeglasses made with the framed lenses hinged to fold into a handle, used by holding the lenses to the eye instead of wearing them as spectacles or pince-nez.
Lossier curve – The technical terminal curves of a Breguet hairspring.
lost wax casting – A process of casting whereby a wax model is encased in an investment similar to plastic, the investment is agitated mechanically or put into a vacuum to remove air bubbles and placed in an oven where the wax is burned off, leaving a cavity which is filled through an opening with molten metal. Then the investment is broken away from the hardened metal, which is ready for polishing and stone setting. For large-scale production, numerous identical wax models are made by pouring molten wax into a rubber mold; all are placed in the investment as a tree-like group. This process is also known by its French equivalent, cire perdu.
lot pearls – Small pearls, below 1 carat in weight.
Louis XIV hands – A style of clock and watch hands designed in the manner of the period of Louis XIV of France. For illustration, see HANDS.
loupe – A jeweler’s or watchmaker’s magnifying-glass worn over one eye; with a single lens or a system of lenses for greater magnifying power.
loupe clean – A term used to describe a diamond that shows no flaws under magnification; its misuse to deceive is prohibited by the Federal Trade Commission; the American Gem Society prohibits its use by members. See FLAWLESS.
love arrows – Sagenitic quartz.
love stone – Aventurine quartz.
lower girdle facets – The 16 triangular facets that border the lower side of the girdle of a round brilliant cut diamond. Before about 1935, they often were cut to form points half way down, between the eight pavilion facets. But current practice is to lengthen them to approximately 80 per cent of the girdle-to-culet distance, for an increase in brilliance with some loss of weight. Also called bottom-half, bottom-break, lower break facets. See GIRDLE FACETS; BRILLIANT.
low relief – A form of ornament in which designs are raised above a background surface, but raised less than one-half of what would be their full “thickness;” for instance, of a human face on a cameo. This is often stated as bas-relief. See HIGH RELIEF. 2. The appearance of an inclusion in a gem with a refractive index near that of the host material.
low – square setting. A replica of the upper half of a square prong setting. Frequently used for repair or replacement jobs.
lozenge – 1. A fancy diamond cut, like the diamond of a pack of playing cards, in outline. 2. A diamond-shaped decorative motif. 3., Facet.
lozenge graver – A graver of diamond-shaped cross-section, affording a long slim point, for cutting inside a narrow space.
L-rest – Hand rest, L-shaped to allow closer entry of cutting tool into a recessed area.
L.S.I – Large scale integration. Type of sophisticated circuitry in quartz timepieces.
lucky stone – Twinned staurolite.
lug – 1. The extensions of a watch case to which is secured the bracelet. 2. The spring bars attached to the lugs.
lumachelle – Fire marble, fossiliferous limestone with the preserved, unaltered, iridescent shells of molluscs, usually ammonites or baculites. See AMMOLITE.
luminescence – The emission of visible rays by certain stones or other materials that have been excited by invisible rays. The phenomenon is called thermoluminescence if the stimulus comes from heat rays beyond the red end of the spectrum; triboluminescence, if the light results from impacts. The phenomenon is called fluorescence if it coincides with the stimulus of rays beyond the violet end of the spectrum, and phosphorescence if it persists after the removal of that stimulus.
luminous dial – Any dial the indicators of which are coated with material that glows in the dark, often radioactive until the Nineteen Thirties, thereafter of some non-radioactive material such as tritium or other phosphorescent exciter.
luminous hands – Watch hands made of skeleton form, the openings holding a filling of a phosphorescent exciter, for use with dials with luminous numerals. For illustration, see HANDS.
lumpy. A stone which is cut so that it has too much depth for its spread.
lumpy girdle – Too thick a girdle.
lunar disk – The moon phase disk in a timepiece.
lunar stone – A phosphorescent variety of barium sulphate, barite. See PHILOSOPHERS STONE.
lunette – A watch glass with slight top curve but sharply curved at the edge.
luster – 1. The appearance of a surface in reflected light, divided into two principal groups, the metallic and the non metallic. Non-metallic lusters may be vitreous, resinous, pearly, greasy, silky, or adamantine. Minerals with refractive indices from 1.3 to 1.8 will have vitreous luster, from 1.9 to 2.5 adamantine luster. Pearly luster is seen on the cleavage planes of minerals having pronouncedly good cleavage, silky luster in minerals with a fibrous structure. 2. Pearl By blocking the light source with one’s head and holding a strand 6-9″ in front of the eyes, the head and shoulders may be seen reflected in a lustrous pearl. The GIA appraisal system uses six grades of luster: Very Bright, Bright, High, Medium, Slightly Dull and Dull. Most strands fall in the Medium range. 3. Diamond. Diamond’s adamantine luster gives it a brilliance unobtainable in other stones. No substance can be polished more highly or keep its polish so long against every adversary.
lute – A refractory cement or clay for packing a joint or sealing a cover to a crucible. 2. Luting, to protect parts from heat when soldering by coating with lute.
lychnis – Ancient name for a red gem stone, either spinel or rubellite. Suspected to be the latter from Pliny’s description of it as a stone which attracts chaff and bits of paper when heated in the sun or by friction.
Lydian stone – Touchstone.
lyncurion, lyncurium – An ancient Greek name, mentioned by Theophrastus, for a brown gem, possibly zircon, which was supposed to have been formed from the congealed urine of the lynx.
lynx eye – Labradorite with a green schiller color.
lynx sapphire – Said to be applied to a light blue sapphire or, more fancifully, to cordierite. Another authority applies it to dark blue sapphires. Neither usage is desirable.
lynx stone – Cordierite.
maacle – Same as MACLE.
mabe – Japanese term for half-pearls, pearls that have been cultured against the shell so that only a hemisphere of nacre grows. They are cut out and often backed with a lower half of mother-of-pearl cut from a large Margaritifera shell, to make an apparent round pearl and then mounted in a setting, like a ring, which requires only an upper half to show.
Macassar shell – Mother-of-pearl shell coming from the northern and western coasts of Australia, Margaritifera maxima, the largest pearl oyster, which also lives along the Malay coast and which is named according to the trading center. Also known as Sydney, Queensland, Port Darwin, New Guinea, West Australia, Manila or Merghui shell. Slight differences characterize the localities; the Australian is uniformly silvery white, the Macassar is more iridescent, and the Manila has a wide yellow border.
Machastone – Moss agate.
macle – (mahkl) 1. French for twin. Many mineral crystals are intergrown in twin relationships, but the trade, speaking of macles, means diamonds which are twinned according to the spinel law. They take the form of flattened triangles and a perfectly developed pair will show re-entrant angles at the corners. The twinned growth breaks the cleavage direction and makes the stones harder to cut into good gems. 2. A classification of rough diamonds, triangular flat stones which are such twinned crystals.
Madagascar amethyst – A distinction which can only be made by experts. Dark amethyst from Madagascar is supposed to have a somewhat smoky tinge; the lighter shades resemble the Siberian, often having a pronounced reddish-violet hue and velvety tone.
Madagascar aquamarine – A trade term for a dark blackish-blue, rather than pure blue, aquamarine.
Madagascar citrine – After Brazil, Madagascar is the most important locality. Said to be somewhat more brilliant and more like topaz in color; the quality is often improved by burning.
Madeira topaz – Misnomer for naturally brown quartz crystals from Spain, the original “Spanish Topaz,” with a Madeira-wine color— the name refers to the color, not a locality. Since 1900 the name has also been applied to the darker burned Brazilian amethyst.
Madras pearl – 1. Persian Gulf pearls, many of which come into the trade through Madras or Bombay. 2. Trade name for selected natural oriental pearls of the highest quality.
magma – (magg’ma) Liquid rock material within the earth from which igneous rock or lava is formed. See IGNEOUS ROCK.
magnetic balance – A watch balance impelled by its magnet’s attraction or repulsion from an electromagnet.
magnetic banking – In an electric watch, the positioning by a magnet of the indexing units.
magnetic chuck – A lathe-chuck holding its objects by magnetic attraction.
magnetic corrector – In astronomical clocks, a permanent magnet attached to the bottom of the pendulum, below which is an electromagnet in which a weak current may be introduced at will, to modify the effect of gravity on the pendulum, to influence the rate of the clock.
magnetic escapement – Any electrically motivated escapement in which wheels are advanced through magnetic influence.
magnetisation – Horology. The condition a watch may be in from too close proximity to heavy electric currents and magnetic fields, in which the steel parts become magnetic, and exert forces on each other that ruin accuracy of timekeeping. Magnetism may be removed rather easily by demagnetizing. See DEMAGNETIZING.
magnetostrictive – A change in dimensions in a ferrous metallic transducer under magnetic influence. The metallic transducer in some ultrasonic cleaning machines.
magnifier – See LOUPE.
maiden pearl – A newly fished pearl.
main facets – The bezel and pavilion facets of a brilliant-cut diamond.
mainspring – The spiral coil of steel “ribbon,” the unwinding of which furnishes motive power for portable timepieces. The first use of a spring for this purpose was made by Peter Henlein, of Nurnberg, Germany, shortly after the year 1500, who thus made the first watch. About the middle of the 19th Century, the trend began of making mainsprings longer and weaker, replacing the shorter, thicker springs with which, for the previous three centuries, had to be used the FUZEE or other power-equalizing device, to compensate for the great difference in power with the spring fully wound or nearly run down. The more modem idea is to use a spring running much longer than just about a day, so that its weaker phase is not reached by the time it should be rewound, in this way obtaining more uniformity of power, A matter that helped in doing away with the fuzee and using longer mainsprings was the discovery of adjusting to isochronism, which made it less essential to seek uniformity of power and the unattainable uniformity of arcs of balance motion. See FUZEE; HENLEIN; ISOCHRONISM.
mainspring barrel – A casing of metal, recessed out to contain the mainspring of a timepiece, with or without its outer rim cut with gear teeth to form the “first” wheel in the train. See GOING BARREL; MOTOR BARREL. mainspring brace. A metal part attached to the outer end of a mainspring, to strengthen the hold of the outer end of the spring in the barrel rim, by engaging in slots in the barrel bottom, or cover, or in both.
mainspring gauge – An instrument for measuring the thickness and width of watch mainsprings. The principal types are notch gauges, and simple forms of jaw-gauges. Watchmakers are more and more adopting machinists’ micrometer calipers for gauging mainsprings in fractions.
mainspring hook – A metal hook either on the periphery of a barrel arbor hub, or inside the rim of the barrel, engaging in a hole at either end of the mainspring, to hold the spring in action during the winding and running of a timepiece.
mainspring punch – A special pliers with a variety of dies and punches for quickly piercing holes in ends of mainsprings for engaging the hooks of barrels and arbors.
mainspring winder – A tool for winding a mainspring for replacement in its barrel, instead of twisting the spring into the barrel with the fingers, which may result in malformation of the spring coil.
maintaining power – Horology. Mechanism of various designs for providing motive power to keep a clock running during winding, when winding would place a reverse direction of power on the train and stop the clock, in the absence of maintaining power mechanism.
main wheel – In the gear-train of a watch or clock, the toothed wheel which forms a part of the first mobile in the train. In clocks the main-wheel is on the weight-cord drum or mainspring arbor; in modern watches on the mainspring barrel. The main wheel is the “first” wheel of the train; usually the center wheel is second, and so on.
Majorica – The trade name of a particular brand of imitation pearls manufactured in Majorca, Considered by their makers to be superior to ordinary imitations, they are intensively advertised and the name is protected, but unsophisticated buyers are often led to buy imitation pearls made in Majorca under the illusion that they are this particular manufacturer’s product.
make-and-break – Attachment to a clock or chronometer, a special switch to obtain electric impulses for actuating a recording chronograph, or to make sound-signals.
malachite – (mal’a-kite) A soft green basic carbonate layers and so exhibits a banded appearance when cut and polished. It is an important ore of copper at some localities. See AZURITE.
malacolite – (mal-lak’o-lite) Diopside.
malakon, malacon – A brown glassy variety of zircon.
male sapphire – A darker colored stone, as opposed to the lighter, known as female. The sexual attribution of gems is supposed to have been started by Theophrastus, who developed a theory of stones’ breeding.
male stem – A winding stem for a watch in which the square on the stem fits into a hollow square in a bevel or clutch pinion in the watch movement.
malleability – Property of some metals of being extended or shaped by beating with a hammer, or by the pressure of rollers. By hammering, gold is the most malleable of all metals, having been beaten into leaves 1/300,000 inch thick. However, by rolling, lead takes first place; gold, third, See DUCTILITY.
mallet – A hammer with a heavy head made of non-metallic material, used for cold-forging operations on soft metals, etc., to avoid denting the work as would be done by a steel hammer. Jewelers use mallets with heads of tightly bound rawhide, in connection with a steel mandrel, for forming and sizing rings.
maltesite – Chiastolite.
Maltese cross stop-work – A device used mostly in high-grade Swiss watches for limiting the run of the mainspring to the force delivered by the coils when neither fully wound up nor run down. Name derived from the resemblance of the “star-wheel” to a Maltese cross. See FUZEE; MAINSPRING; STOP-WORK.
Manchurian jade – A hard brown soapstone.
mandrel – 1. An arbor on which work to be formed in a lathe or other machine is mounted to support and rotate the work during cutting, grinding, etc. The work is usually such as has a hole in it through which the arbor passes friction-tight. 2. A steel rod slightly tapered, used by jewelers as an anvil for forming rings by blows with a rawhide mallet. 3. A watchmakers’ lathe of Swiss origin, used exclusively for flat facing turning such as recesses in watch plates; has hand-driven universal face-place, and slide rest; has no facilities for other work than above stated. See LATHE.
manganese garnet – Spessartine.
manganese spar – Rhodochrosite.
manganese silicate – Rhodonite.
mantle – The outermost tissue layer of a pele-cypod which contains nacre-depositing cells.
manufactured stone – Gemology, Any kind of an artificial stone; synthetic, imitation, etc
Manufacturing Jewelers and Silversmiths of America, Inc – A national association of more than 1000 manufacturing jewelers and silversmiths, headquartered in Providence, R.I.; founded in 1903; publishes monthly American Jewelry Manufacturer; sponsors trade shows in Providence, New York and elsewhere.
Maori stone – Nephrite.
marcasite – (mar’cass-ite) Trade term for cubic pyrite crystals, mounted in groups, cut or uncut, in pins and other pieces of jewelry. An iron mineral with bright metallic luster, its hardness is 6 to 6’/2, its specific gravity 4.9 to 5.2. Source, South Tuscany, Italy; cut by semi-automatic machinery in Turnov, Czechoslovakia, and the Jura Alps, France. Mineral-ogically speaking, the term marcasite is applied to another iron sulphide which has the same chemical composition as pyrite; resembles it in color, luster and hardness; but crystallizes in the orthorhombic system and has fewer specimens suitable for cutting.
marekanite – A decomposing perlitic obsidian, clear pebbles of which, gray, brown, yellow and red in color, are found along the banks of the Marekanka River in eastern Siberia.
Margaritifera – A pelecypod genus to which the precious pearl-bearing oysters belong. Different strains produce recognizably different color varieties. Mgarcharium pearls are yellow (Shark’s Bay, West Australia), M margaritifera are silver white (north coast of Australia; shell is largest and more important than its pearls), M. martensii pearls are greenish white (natural pearls from Japan; cultured pearls in this oyster are white), M. maxima are silver white (North Australia), M. vulgaris pearls are pale creamy white (Gulf of Monaar).
maria glass – An early name for mica and selenite.
marialite – The sodium end-member of the scapo-lite mineral family.
Mari diamonds – Misnomer for rock crystal from near Kalabagh and Mari, India.
marine chronometer – A very accurate portable timepiece used for navigation of ships, for carrying the time of a known meridian to use in connection with local time of the ship’s position obtained by observation with a sextant. The main characteristic of marine chronometers is their escapements, which are of the detent type. See CHRONOMETER; DETENT; ESCAPEMENT; NAVIGATION.
Marmarosch diamond – Misnomer for quartz.
marquise – A design of setting for cluster stonework in rings, etc., in which the stones are set in a pattern like the outline of a marquise-cut diamond.
marquise cut – (mar-keez’) An elongated, doubly-pointed variation of the brilliant cut, a popular diamond shape.
Mascot emerald – Trade name for an emerald triplet, supposedly made from genuine beryl. If any of these are in the trade, they are very rare; quartz is the common material used in emerald triplets.
mass aqua (marine) – Popular name for a hard glass imitation of aquamarine with a hardness of 6, and a refractive index of 1.50.
massive – In reference to a mineral, one speaks of non-crystallized, though often crystalline, material as massive.
massive amber – A compact variety of Baltic amber.
mass opal – Opal matrix.
master clock – In a system of a number of clocks corrected or operated by an electric circuit, the master clock is the one, at a central point of the system, whose timekeeping rate is conveyed to all of the secondary clocks on the circuit. In synchronous electric clocks, driven by domestic service current, the master clock at the power plant regulates the speed of the generators so they will deliver the alternating current at the correct rate of cycles per second for which the secondary clocks are designed.
Matara diamond – Also spelled Matura; misnomer for zircon.
matching – Horology. A term used in watch factories denoting the adjustment of the escapement, as one of the processes of assembling or “finishing” watches. In the watch repair trade, this work is called escapement adjusting.
materials – Horology. Replacement parts for repairing watches and clocks, as kept in stock for sale by “material houses” or dealers.
matinee length – Pearl necklace, 22″ to 23″ in length. See PRINCESS; CHOKER; OPERA LENGTH.
matrix – (may’trix) The rock in which the gem is imbedded, often some of this is polished along with the gem to make such stones as opal matrix, turquoise matrix, emerald matrix, etc.
matting, matt-finish – A finish given to a metal surface by producing on it a multitude of small pits, making a frosted or grained appearance, instead of polished or line-finished. See LINE FINISH; SANDBLASTING.
Matura diamond – Misnomer for colorless zircon, mostly heated stones though some naturally colorless stones may occur in the southern part of Sri Lanka known as Matara. Colorless zircons in small, almost microscopic, crystals are common in many rocks and their derived sands.
mauve jade – A pale lavender color phase of jadeite.
maxixe aquamarine or beryl – A name which has been applied to a deep blue, boron bearing beryl from the Maxixe Mine, Minas Gerais, Brazil. It is strongly dichroic in pink and blue. All are said to have faded after a short exposure to light, and the color can be restored by irradiation in this particular type of aquamarine. Deep blue aquamarines, even those naturally deep blue, are consequently suspect, for paler blue aquamarines of this type could, for a time, be made to look darker by an irradiation treatment.
mayaite – (my’a-ite, not may’a-ite) Name proposed for the Central American jade rock, which is chemically unlike that of the Orient. It differs in the presence of considerable amounts of diopside, the magnesium silicate, with the jadeite molecules, and usually there is more or less albite in solid solution with the pyroxene. It varies in color from white to yellow green and gray green. The locality from which it comes is unknown, probably one or two places on the Pacific coast of Central America. See MEXICAN JADE; TUXTLITE.
Mazarin cut – A 34-faced rather blocky brilliant type of diamond cut commenced in the middle of the 17th Century under the aegis of Cardinal Mazarin.
mean-time screws – Screws with threads fitted friction-tight in a balance rim, to be turned in for regulating watch to go faster, or turned out to go slower. Usually there are two meantime screws, located at the ends of balance arms; occasionally, two additional screws each half-way between ends of balance arms.
mechanical advantage – The ratio of the expending working force to the force applied to a mechanism.
mechanical dop – See DOP. A mechanical dop is a small vise in which the stone may be held at any angle, held in place by jaws and fastened by a bolt, in place of the older method of embedding the stone to be cut in a low melting point solder.
medfordite – Local Oregon name for a massive white quartz with streaks and patches of green and brown moss.
Medina emerald – Misnomer for a green glass imitation stone.
mega – A million times a given unit (cycle, ohm, watt, etc.).
meionite – (my’on-ite) The calcium endmember of the scapolite family of minerals. See MARI-ALITE.
melange – Assortment of mixed sizes of diamonds, larger than melee.
melanite – (mell’ann-ite) A black andradite, but probably the stone has never found any gem use.
Meleagrina pearl – (mel’e-a-green”a) Synonymous with Margaritifera.
melee – (mell’ee—anglicized pronunciation) Term derived from French word for “mixed,” now generally applied in the diamond industry to round diamonds, whether graded and sized or not (single, Swiss or full-cut), up to 1/6, 1/5 or even 1/4 carat in size. Diamonds larger than melee are called SIZES. The term SMALL MELEE or SMALL is often applied to diamonds weighing I/16th ct. or less; these commonly have only 18 facets, including table and culet, although fully-cut 58-facet stones are commercially available as small as I/100th ct. See FULL-CUT; SINGLE-CUT; SIZES; SMALLS; SWISS CUT. The embellishing diamonds mounted in any article or jewelry are collectively classed as melee.
melichrysos – (mel-i-kris’os) Ancient name for yellow zircon.
melle – Brazilian term for poor quality diamonds.
melting snow jade – Fanciful name for a jadeite quality which is characterized by a white to gray color, with irregularly distributed opaque white patches veined and cut by more translucent streaks. The name is apt and well de¬scribes the appearance.
menilite – (men-ill ite) An opaque gray or brownish common opal which takes a fine polish, occurring in colloform masses at Mont Menil in Paris.
mercurial gilding – See MERCURY GILDING.
mercurial pendulum – A compensating pendulum, invented by George Graham, about 1715, the bob of which is a vessel containing a column of mercury. As increase of atmospheric heat lengthens the pendulum rod, it also raises the centre of mass of the mercury column, which compensates for the lengthening of the rod, and vice-versa. Adjustment comprises adding or removing mercury, until compensating effect is correct. See GRAHAM, GEORGE; PENDULUM.
mercury – A white elemental metal, which is liquid at ordinary atmospheric temperatures. In horology, it is essential for mercurial compensating pendulums and mercurial switches.
mercury contact – An electric switch for obtaining a record of pendulum vibrations, or other purposes in clockwork, having a metal point on the pendulum to sweep through a cup of mercury; or a sealed tube of mercury which tilts with the movements of the pendulum and opens and closes a circuit between points inside the tube.
mercury gilding – This, the oldest gilding process, used since Roman times, was the chief method by which metals were coated with gold before the invention of electroplate. An amalgam of gold dissolved by mercury (about one-third mercury and two-thirds gold after final treatment) and a solution of nitrate of mercury were brushed repeatedly upon the work, which was then heated over charcoal until the mercury was driven off, leaving a deposit of gold. The gold formed an alloy at the point of contact, making a tough, cohesive coating. The layer could be varied in thickness, so that it was possible to coat the other metal with a heavy deposit of gold. Because poisonous fumes took the lives of many craftsmen, the process was outlawed in several countries. See VERMEIL.
Mergui shell – Shell of the M. maxima species marketed in Burma.
metallurgy – The art and science of extracting metals from their ores and preparing them for use by the manufacturer, who fashions them into finished articles. It includes smelting, amalgamation, electrolytic refining, etc.
metamorphic – Literally, changed form. In geology metamorphic rocks are those which have been altered from their original character (usually sediments) to an igneous rock mineral makeup by heat and pressure within the crust, consequences of mountain-making forces. Migrant volatiles play their part in this high-temperature reshuffling of elements.
methyl alcohol – Chemical term for wood alcohol. Important in horology and jewelry work mostly as the substance added to pure grain alcohol (ethyl alcohol) to make denatured alcohol, which is used for rinsing cleaned watches, jewelry, etc.
methylene chloride – A colorless volatile liquid used as a degreaser or refrigerant. Will also melt many plastics.
methylene iodide – (meth’ill-een) An expensive organic iodine compound with a high refractive index (1.742) which is used when testing gems on the refractometer, and a specific gravity of 3.324 making it valuable as heavy liquid for gravity determinations.
metric carat – The present internationally ac¬cepted unit of weight for gem stones, 200 milligrams or five carats to the gram.
metric grain – A pearl weight, equal to one-quarter of a metric carat.
metric measurement – Measures of length based upon the meter, with units or subdivisions expressed in multiples of ten. In horology, it is especially convenient to use the millimeter (one thousandth of a meter) and its divisions of tenths and hundredths. It is far easier mental arithmetic to measure most parts of a watch in a few millimeters and decimal fractions, than to use the inch and thousandths. The latter usually requires use of odd figures in three places, for sizes of watch parts.
Mexican agate – Any of many colorful varieties of agate, generally occurring in smaller nodules than the Brazilian ones, but much more attractively banded and not in need of the dyeing customary with Brazilian agates. Also, a misleading term which has been applied to banded calcite or aragonite onyx, which, by contrast, is often dyed.
Mexican black diamond – Misnomer for hematite.
Mexican diamond – Misnomer for rock crystal.
Mexican jade – A true jade, one of the few known occurrences of the mineral jadeite, and extensively used by the pre-Colombian Mexican Indians. Apparently found like the Burmese jadeite in loose boulders, but long known only in worked objects. See MAYAITE and TUX-LITE. However, utmost caution should be observed in the use of the term, for in recent years a calcite onyx-marble, dyed green, has been widely sold in silver jewelry under the misleading name of “Mexican jade.” It is soft and easily scratched with a knife. It effervesces in hydrochloric (muriatic acid), and is thus easily distinguished from the hard and insoluble true jade.
Mexican onyx – Banded yellowish, greenish calcite or aragonite commonly used in ash trays and decorative objects. The Mexican onyx seen in the trade mostly comes from Argentina.
Mexican opal – Precious opal mostly from Queretaro, Mexico. It is characterized by a fine fire and an almost transparent body, which may be colorless, slightly golden or slightly red, grading into FIRE OPAL with a strong body color and no color play. It occurs in pockets in a reddish igneous rock, bits of which are often polished with the stone.
Mexican pearl – Pearl from the Gulf of Mexico, supposed to be unusually larger but less well-shaped and somewhat duller in color than oriental pearls. Also called OCCIDENTAL PEARLS
Mexican turquoise – A misnomer; no important turquoise occurrence is known in Mexico; probably intended for western U.S. turquoise. In general this material is likely to be a little lighter and greener than much of the oriental, and to have a brown-to-white matrix.
Mexican water opal – Mentioned by G. F. Herbert-Smith without definition, it probably means the colorless transparent precious opal, characteristic of the Mexican occurrence.
MI – Abbreviation for “moderately included.” See CLARITY GRADE.
mica – (mike’a) A group of minerals, including several varieties known as MUSCOVITE, BIOTITE, PHLOGOPITE, etc. They are important rock-making minerals and have numerous industrial applications when found in large sheets. Hydrous aluminum silicates with potash, iron, magnesia, etc., they are characterized by a good cleavage, and great flexibility. LEPIDOLITE, a purple lithium mica often associated with tourmaline, has been cut into decorative objects. FUCHSITE is a muscovite with green coloring from chromium which gives aventurine quartz its color. Some AGALMATOLITE is made of a fine-grained massive mica.
mi-concave – A form of watch glass or crystal, for open-face watches, in cross-section appearing of uniform thickness throughout its “arch” with sloped, straight-beveled sides to form clearance to fit in seat of bezel. One of the oldest forms of watch crystals, but never entirely out of use as some other forms have become.
micro-chronograph – A device used in connection with astronomical clocks, for recording thousandths of a second.
microcline – (my’kro-kline) The tri clinic potash feldspar characteristic of acid pegmatite dikes. It is often green, as well as pink, cream, and white. The green variety is known as AMAZON STONE and is widely used as a decorative material. The other varieties, more common, constitute most of the feldspar used commercially in ceramics and scouring powders.
micrometer – A measuring instrument in which the object to be gauged rests on a stationary block surface or “anvil” at one side, while against the other side is brought up the end of a screw, which has a head graduated on its rim, from which the measurement is read. With the screw-end against the anvil, the screw-head graduation reads zero; as the screw is turned to open the space between anvil and screw-end, each complete turn of the screw is indicated by graduation on a tube (“sleeve”) surrounding the screw, and subdivisions of each turn are indicated by graduations on the “thimble” which acts as the screw head. All the graduations are based on the pitch of the screwhead for the screw advances lengthwise, per turn, exactly the distance between the tops of two adjacent threads. Micrometer calipers are made in inches, thousandths and ten-thousandths; and in metric measure in millimeters, tenths and hundredths. The use of metric micrometers for watchwork is increasing. See METRIC MEASUREMENTS; MILLIMETER.
micrometer regulator – A regulator in a watch or portable clock, in which the index-hand is moved by turning a screw instead of directly by pushing it with a tweezer, etc.
microminiaturization – The process and technique of producing machines or devices to operate effectively in a fraction of the area formerly occupied.
micron – Unit of measurement, 1 millionth of a meter, or 1 thousandth of a millimeter.
middle temperature error – In watches with bimetallic compensating balances and steel hairsprings, even if adjusted to temperature so well that they would keep time alike at the extremes of heat and cold, there will in all cases be a gaining error at points of temperature between the extremes. This is due to a difference in these two things: (1) the effect of changes of heat and cold on the elasticity or “force” of the hairspring; and (2) the effect of changes of heat and cold on the bending of the rim-segments of the compensating balance. That is, the changes in hairspring and in balance, caused by temperature, do not progress in both of them at the same rate, with the rise and fall of the thermometer, so that perfect adjustment to all degrees of heat and cold is impossible, and the middle temperature error is the result. Obviously with a hairspring not much affected in timekeeping rate by temperature, compensation is proportionately unnecessary, and middle temperature error practically non-existent. These conditions are met commercially by the watches now being made with hairsprings of alloy metals relatively unaffected by heat and cold, and
midge stone – MOSS AGATE.
milk glass – Opaque glass in a milky-white color.
milk opal – Milky white common opal with which is associated the precious opal in Australia and Hungary.
milky quartz – Opaque to translucent white coarsely crystalline quartz, commonly occurring in veins. Gold matrix specimens are usually composed of gold in milky quartz.
mill – Metal work. 1. A cutter for forming gear-teeth or other work, with numerous teeth with profiles of the form to be produced, used on a rotating spindle in an attachment to watchmakers lathe. 2. A pair of steel rolls to rotate opposite to each other, used in jewelry shops for reducing thickness of bars of metal.
Miller process – A method of refining gold by passing chlorine gas through the molten metal. Base metals and silver are converted into chlorides which rise to the top as fumes or slag.
millgraining – A detail of gem-stone setting, the formation of beading, or a set of very small hemispheres in procession on the top of a knife-edge of metal in the design of the setting. The beading is produced by a steel roller with female beading sunk around its periphery, the roller set in a handle which allows it to be pressed forcibly against the work, while advancing it along the work.
millgrain knurl – A millgrain wheel. See MILLGRAINING.
milliamperes – The thousandth part of an ampere.
millimeter – Unit of length measure, one thousandth of a meter. A millimeter is .03937 inch. See METRIC MEASUREMENT.
mineral – A naturally occurring inorganic substance with fairly definite physical properties and a chemical composition varying within certain limits.
mineralogy – The study of minerals.
mineral turquoise – A term sometimes used to accentuate the distinction between TURQUOISE and ODONTOL1TE.
minute – 1. One-sixtieth of an hour of time. 2. One-sixtieth of a degree of arc.
minute-impulse relay – An electric relay for obtaining an instant change of minutes in time-stamping clocks.
minute-jumper dial – On a watch or clock, a dial which has instead of a graduated circle and hand, an opening in which appear numerals indicating minutes, which are painted on discs rotating under the dial and moved by click-and-ratchet mechanism.
minute pinion – In a dial train, the pinion fastened to the minute wheel which wheel is turned by the cannon pinion; the leaves of the minute pinion engage the teeth of the hour wheel. See DIAL TRAIN.
minute recorder, register – An attachment to a chronograph watch which indicates on a dial the number of minutes during which the fifth seconds hands have run between starting and stopping them for an observation.
minute repeater – A complicated watch which will strike time to the minute whenever a slide on the case is pulled; the highest form of repeater. Less elaborate mechanisms are repeaters that will strike the nearest quarter-hour; or the nearest ten minutes after the hour.
minute track – The 60 markings in the ring around a timepiece dial.
minute wheel – In a dial train, the wheel with teeth engaging the leaves of the cannon pinion, and with a pinion fastened to it which turns the hour wheel. See DIAL TRAIN.
miter gears – Bevel gears of equal diameters. S gears are used in some varieties of stem wing and setting work.
mixed cut – A combination-type of cutting, crown being slightly higher and the table larger than in a normal brilliant, and the pavilion step-cut, with the same number of facets as in the crown. The form is used to give the color obtained with the step-cut some of the fire which is found in the brilliant cut. Fancy sapphires are often cut in this style. See FRENCH CUT; BRILLIANT CUT; S CUT.
mobile – Horology. Generic term often applied to any and all of the parts of a timepiece turn on the pivots, and more specifically, the arbors carrying wheels and pinions.
mocha stone – MOSS AGATE.
mock pendulum – In old bracket clocks, a n disc on an arm of the actual pendulum motions visible through an aperture in dial; to give a pleasing appearance of “life the clock.
model – In jewelry, an original piece from which a mold is made to cast wax patterns. May be made by “building up,” as in making a piece of fine jewelry; by “cutting down,” making white metal models, or by carving building up in wax.
module – In wheelwork, the result of div: the pitch diameter by the number of feet. A replaceable unit containing a group off as in electrical watches.
Moebius process – Method of refining silver tainting small amounts of gold. Anodes of pure silver are electrolyzed in an acid silver nitrate bath; pure silver is deposited on a cathode of sheet metal.
Moe diamond gauge – A gauge involving calipers and a table, designed by Charles Moe for the determination of approximate weights of brilliant-cut diamonds.
Mogok – District in Upper Burma, which, since the 15th Century, has produced rubies, including the best pigeon-blood red, besides spinel, sapphire, zircon and tourmaline.
Mogok diamond – Local Indian name for colorless topaz.
Mohs’ scale – A scale of relative hardness for use in testing minerals. Named for the German mineralogist Friedrich Mohs (1772-1839), who proposed it in 1822. The minerals are numbered, but the intervals between them are very different, and diamond is far far harder than corundum, as much harder as corundum is than talc. Minerals vary in hardness in different crystal directions, calcite for example can be scratched by the finger nail on the face which truncates the three cleavage rhombohedra. See WINCHELL HARDNESS SCALE.
Mojave moonstone – (mo-haav’ee) A gray translucent chalcedony, the name is used to distinguish this from “blue moonstone,” pale blue, and “California moonstone,” white. All these terms are misleading and undesirable.
mold – 1. A hollow form which gives shape to metal in its molten state. 2. In costume jewelry, a fairly hard rubber form into which white metal is cast directly. 3. A bronze or iron form into which metal is cast. 4. A separated form made of sand or cuttlefish bone, into which metal is cast. 5. A flexible rubber form into which casting wax is forced to make an expendable pattern. 6. A sectional, low-fusing metal form used for casting wax patterns of superior dimensional stability. 7. A refractory form into which molten metal is forced under pressure to produce intricate castings.
moldavite – (mole’dav-ite). A light green glass of natural but unexplained origin. Originally thought to be volcanic glass, discoveries of the stone in parts of the world where no volcanic activity has recently occurred, have led to the theory that they represent meteoritic glass. Moldavite is found along the Moldau in Bohemia, hence its name. It is also known under many erroneous or misleading names such as Bohemian chrysolite, bottle stone, chrysolite, pseudochrysolite, false chrysolite, or water chrysolite.
molding – See CASTING.
mold frame – A metal block with an opening the size of the desired mold. Into this opening rubber is vulcanized around a metal model to form the rubber mold.
mold mark – A seam on a piece of glassware, indicating the piece was formed in a mold. When the piece is well finished, the mark should not be obtrusive.
mold rubber – A highly flexible latex rubber used in making rubber molds. Vulcanizes at approximately 300°F.
mole-stone – Ancient, perhaps Roman, glass bead found in the earth and believed by the superstitious to have certain magical properties. Toadstone, snail-stone and adder-stones were the same.
molochites – Ancient name for green jasper.
molybdenum bi-sulphide, di-sulphide – A soft graphite-like mineral used as a lubricant in watches and clocks.
monazite – A Bolivian variety of this rare earth phosphate looks pink under incandescent light, dark green in daylight or fluorescent light; not found in gem sizes.
Monel metal – A tough nickel-copper alloy gray in color. Melting point: 2370°F.
monitor lathe – Lathe with revolving slide rest multiple tool-holder, for turning successively a variety of forms on one piece of work; the basic principle of nearly all machines used in watch and clock factories in mass-production of parts for timepieces.
monochromatic – (mo’no-kro-matt”ik) Of a single color. A monochromator is actually a sort of spectroscope so designed that only a narrow band of light of one or another wave-length (hence color) is emitted at any one time. Useful in gem testing when sodium light wavelengths are needed, or some other standard wave-length.
monoclinic – A crystal system, in which there are three unequal axes, two of which are at right angles to each other, and the third inclined to the plane of the other two. Diopside, epidote, spodumene and sphene crystallize in this system.
monometallic balance – A watch balance made of one metal throughout, used in combination with a hairspring of alloy metal in which there are practically no changes of elastic force under changing conditions of heat and cold. A monometallic balance does not compensate because with its hairspring compensation is not needed. See BI-METALLIC BALANCE; COMPENSATION; MIDDLE TEMPERATURE ERROR.
monster-pearl – Round pearl of exceptional size, also known as a paragon.
Montana jet – Obsidian.
Montana ruby – An infrequent hue in the Montana sapphires, but some are red enough to be accepted, especially locally, as rubies.
Montana sapphire – In trade terminology, a Montana sapphire is a blue sapphire which is lighter and more steely in color than the Kashmir and Ceylonese. However, many fancy-colored sapphires are found in Montana and there might be some danger of confusion by the use of Montana as a geographical modifier as well as a descriptive adjective.
Mont Blanc ruby – Misnomer for a reddish quartz. See RUBASSE.
Montgomery dial – A design of watch dial, especially for railroad watches, with numerals representing each minute, outside the minute-circle, and very bold hour-numerals; intended to aid quick and exact reading of time; introduced by Chief Time Inspector Montgomery of the Atchison Topeka and Santa FeR. R. about 1895.
Moor’s head – Term applied to black colored tourmalines from Elba.
morganite – Pink caesium-bearing beryl, named by G. F. Kunz in honor of J. P. Morgan. Found in California, Brazil and Madagascar.
morion – An old term for very dark, almost black, smoky quartz.
moro – Japanese oxblood red coral.
moroxite – A name originally applied to greenish blue apatite crystals from Arendal, Norway, in reference to their shape, the terminations of which were blunt. Its use has been extended quite unwarrantedly to cover any bluish apatite, regardless of the crystal habit, and most “moroxite” today is of Canadian origin, though little is of gem quality.
morse – A clasp or brooch used to fasten an ecclesiastic cope.
mosaic – Jewelry. Decorative art work, usually of Italian origin, in which a design or picture is formed of bits of colored stone or enamel inlaid in cement, with their flat tops set or ground flush with the surface of the work.
mosaic gold – Karat gold, the surface of which is composed of fragments of red, yellow, green and white gold, in random pattern.
moss agate – A cryptocrystalline variety of quartz, with stains of various types and colors, giving rise to moss, fern or treelike patterns. The black stains are caused by manganese oxide, reds and greens are probably iron. The Montana moss agates are characteristically light yellow, almost white, with black dendritic patterns in them; moss agates from other localities are very different; the well-known Indian moss agate is green.
moss jasper – Name given to a cabochon quartz variety found in the Arizona petrified wood, in which there are bands of opaque-colored jasper with streaks of translucent chalcedony.
moss opal – Opal with markings like moss agate.
mother of emerald – Misnomer for PRASE.
mother of pearl – The iridescent pearly lining of a shell.
motion – Horology. Term used to denote the angular extent of motion of a watch balance or rarely of a clock pendulum, as “a good motion,” “a poor motion,” meaning respectively sufficient or insufficient angular amount of rotation in the action of a timepiece balance. See ARCS.
motion work – Term customarily used in Europe to denote the dial-train of watch or clock. See DIAL-TRAIN.
motor barrel – A watch mainspring barrel designed so that the mainwheel, with teeth engaging the center pinion, turns on the barrel arbor pivots as the watch runs. The other principal type of mainspring barrel in modern watches is the GOING BARREL.
motor-wound clock – A type of electric clock in which there is the conventional train, escapement and balance or pendulum, but in which the mainspring is automatically wound whenever necessary by an electric motor.
mottled stone – Stone with patches of color, not uniform.
mount – A general term to include the metal base, molding, rim, cover clamp, or other accessory by which a utensil of silver, pottery, glass, or other material is decorated and adapted for use.
mountain mahogany – Red OBSIDIAN.
mounting – 1. A piece of jewelry made for stones, complete except for the setting of the stones; ideally designed to bring out the beauty of the stone, secure the stone against loss or damage, and produce a pleasing, well-balanced whole; “an unmounted piece.” 2. Setting or fastening of stones in place is sometimes referred to as “mounting the stones.”
movement – The mechanism of a watch or clock, as distinguished from the case.
movement cover – A glass dome used on watchmakers’ benches, to cover partly completed watches to keep dust off them.
movement holder – 1. A device for holding watch movements during assembly or other work, either a set of blocks with recessed shoulders in the top to hold the movement, one block for each size and shape of movement; or an adjustable clamp device used for many different movement forms. 2. A rack holding a number of watch movements, with hinges so that it may be clamped in various positions, used in watch factories for timing watches while adjusting them to positions.
Mtoroite – A prase-like, deep spinach green chalcedony, somewhat less translucent than chrysoprase, from Mtoro, Rhodesia.
muddy stone – A dull stone, due to lack of complete transparency.
Mueller’s glass – Clear colorless hyalite opal.
muffle furnace – A gas blast furnace with a muffle inside, which is a box made of fireclay or similar material, usually removable for charging and removing work. In horology, muffle furnaces are used for hardening steel; in jewelry shops for enameling etc. There are also furnaces designed for combined use as muffle furnace or crucible furnace, the latter for melting metals in a crucible.
multimeter – An electrical meter capable of measuring volts, amperes, ohms, watts.
multiple case – One of a class of watch cases in which there are more than one separable cases used together. Examples are the pair-case (double); the triple case with an outer case to protect the decorations of the outside one of a pair case; and reversible combination open-face with hunting case watches.
multiplexing – In electronic timepieces, the sophisticated integration of various electronic functions in a small (circuit) area, allowing complex functions in a small watch.
Mumetal – A nickel, iron, copper alloy with high magnetic permeability, used as cores in magnetic balances, pendulums.
muriatic acid – Popular name for hydrochloric acid, which is an aqueous solution of hydrogen chloride gas, used in jewelry work mixed with nitric acid to make aqua regia, for dissolving precious metals; and in horology for making blue-removing solution. See AQUA REGIA; BLUE REMOVER.
muscle pearls – Small distorted pearls found near the muscle of the oyster.
mushroom stud – A hairspring stud shaped like a’ button on a stalk; contained by a cap on the balance bridge pier.
mussel egg – Tennessee name for a fresh water pearl.
mutton fat jade – A pure limpid white variety of nephrite.
Mutzschen diamonds – Misnomer for rock crystal.
myrickite – Common opal or chalcedony with inclusions of bright red cinnabar, the mercury ore. The opal variety is also known as “opalite.” Found in the west in most mercury regions.
Mytilus pearls – (mit’til-lus) Pearls from the Mytilus or common mussel.