waiting-train – Mechanism long used for electrically synchronizing tower-clocks, particularly in England and her colonies.


walrus wheel – Buffing wheel for polishing, especially silver ware; made of tanned walrus hide. See POLISHING LATHE.


Walton filter – A very dark filter glass for the examination of emeralds, looking dark blue in daylight and black in artificial light. Looking through it, an electric light looks pale reddish yellow. Gems seen through it look as follows: green glass, green; epidote, red; dioptase, green; tourmaline, dark green; emerald, reddish yellow; synthetic emerald, stronger red. Not a lens, and very dark and rather difficult to see through. See CHELSEA FILTER; EMERALD FILTER.


wandering-hour watch – A watch without hands; the hour numerals appear in turn and travel around an arc graduated in minutes. Presumed to be more instantly readable; popular about 1700-1725, particularly in England.


warding file – The thinnest form of flat file regularly manufactured, with teeth cut on both sides and edges.


wardite – A hydrous sodium calcium aluminum phosphate, of interest to gemologists because of its occurrence in Utah as an alteration product of the Lucin variscite. Usually it forms banded bluish masses, often circular and appearing in cabochon stones as bluish eyes, adding to the attractiveness of the otherwise monotonously uniform green of the variscite. Other minerals also form in the same way in the variscite, but wardite is the most common.


wart pearls – Baroque pearls.


washer – 1. Timing washer. A thin metal disc pierced with a central hole, used under balance screw to add weight to balance for making watch run slower, or for poising the balance. 2. Case washer. A washer placed under screw holding watch movement in case, to hold more securely.


washings – Sediment from vessels connected with sinks in jewelry shops, in which is contained particles of precious metals from washing polished work, workmen’s hands, etc. The metals are salvaged by chemical treatment, usually by sending the washings to a sweep-smelter’s establishment.


wass – A large triangular diamond cleavage of an octahedral diamond crystal.


watch – A portable timepiece (French, montre; German, die Taschenuhr); today, a timepiece carried in pocket or on person, differentiated from semi-portable timepieces like marine chronometers, navigators’ deck watches, and traveling clocks, that are carried about but not on the person. The origin of the word is somewhat obscure, but seems associated with the early English word (1300-1500) “Wecche,” meaning to alarm or awaken; the earliest watches, made in Germany from about 1500, often had alarm mechanisms. The distinguishing feature of watches, as a development from clocks, was the use of a coiled spring for motive power instead of weights, which made watches portable. See CLOCK.


watch-cleaning machines – Set of jars holding cleaning and rinsing solutions, with electric motor-driven receptacles for watch parts immersed in the solutions. Usually with a heater for drying parts after rinsing, used increasingly after about 1925, for cleaning watches.


watch-jobber – In the U.S.A., a wholesale dealer in watches. In England, a watchmaker who repairs watches.


watchmaker – In present-day usage, one who repairs watches; who is presumably able to make certain parts for any watch, for replacement in repairing it. Differentiated from one who works in a watch factory, doing a single task repeatedly, or operating a machine, neither job involving outright making of entire parts. The “watchmaker” more or less resembles the old craftsman who made entire watches, instead of the factory operative with his limited duties in mass-production industry.


watchmaker licensing – Legislation providing for the examination and licensing of watchmakers “to protect the general public against fraud and incompetence, and to promote skill and competence in the craftsman;” enacted by Wisconsin in 1937, and thereafter by Florida, Indiana, Iowa, Kentucky, Louisiana, Michigan, Minnesota, North Carolina, North Dakota and Oregon.


watchman’s clock – A timepiece carried by a night-watchman, with rotating paper dial, on which marks are made by using keys chained at various points in a building, indicating times when the watchman visited those stations, to check his performance of duties. Also, a clock in an office, with dial to indicate times when watchman has pressed buttons at stations connected to clock electrically.


Watch Material & Jewelry Distributors of America, Inc – An organization, founded in 1946, of distributors of watch materials, tools, supplies and jewelry lines.


watch paper – 1. A circular printed paper bearing advertisement formerly customarily placed inside outer-case of pair-cased watches by shop-owner where watch was repaired. 2. Sheets of close-grained thin paper, about 4-inches square, used in handling cleaned parts of watches during repairing to prevent finger-stains.


watch rate recorder – An instrument for obtaining instantly a record of the deviation of the timekeeping rate of a watch from a standard rate. The standard rate is established usually by vibrations of an electrically driven tuning fork, or by the piezoelectric effect through a quartz crystal. The rate-record is printed on a paper carried by a drum rotated under speed-control of fork or crystal, the amplified beats of the watch operating the “pen” that makes dots on the paper, which turns at rate of 300 times per minute. If a watch is keeping exact time, its beats will coincide with completed turns of the paper, across which the dots will therefore make a straight line. If watch is not keeping time, the line of dots on the paper will not coincide with completed turns, and will run slantwise, the degree of this, shown against rulings on the paper, indicating the amount of error in rate.


watch sizes – A watch movement is measured by gauging it across the dial side of the main (lower) plate through its center at its narrowest width. English and American manufacturers base their measurement upon the full diameter of a round “O” size movement, which gauges 1-5/30 of an English inch. Every progressively larger size is 1/30″ greater in diameter; thus a 1-size movement measures 1-6/30″. A movement one size smaller than the “O” size gauges 1/30″ less (i.e., 1-4/30″) and is called a 2/0 size. All sizes progressively smaller have zeros added to their sizes, as 3/0, 4/0, etc., each being 1/30″ smaller than its predecessor. Swiss, French, Japanese and most other foreign manufacturers use the ligne, one-twelfth of a Paris inch, as their unit. 1/30″ = 0.84664 mm. = 0.3753166 French lignes. 1 French ligne = 2.25583 mm = 0.088814″.


watch train wheels – In standard design of watch movement, the toothed wheels are named in order, starting at barrel; main wheel (the barrel itself); center wheel; third wheel; fourth wheel; escape wheel. In the numbering, the barrel is considered, but not named, the first wheel; the center wheel, the second wheel. On wheels that have pinions attached, the pinions take the name of the wheels. In the dial train, the pinion on center post is the cannon pinion; it turns the minute-wheel whose pinion turns the hour-wheel. Another name used for minute wheel and its pinion is intermediate wheel and pinion.


water – A term popular with novel writers, referring to the clarity of a diamond, both its lack of color and freedom from flaws.


water agate – Wax agate.


water chrysolite – Moldavite.


water drop – White topaz.


water drop quartz – Quartz, rock crystal, with movable water bubbles, a fairly common phenomenon.


water gilding – A method of immersing base metals into a solution containing gold chloride; the resultant coating is thin, easily wears off.


watering – A decorative finish on nickel watch plates; a variety of damascening in which the graining consists of narrow bands in waving form, the adjacent bands all touching, without any background of other kind of surface finish. See DAMASCENE.


water-opal – A term which has been applied to perfectly clear precious opal, which, nonetheless, shows good fire. Much of the Mexican opal is of this type. There are varieties of water-clear opal without fire, hyalite, with which this might be confused, hence it is an undesirable term.


waterproof – Term currently disallowed by the Federal Trade Commission to describe a watch whose case is impervious to moisture. See WATER RESISTANT.


water resistant – Term allowed by the Federal Trade Commission when a watch has passed a test in which it is immersed in water at normal pressure (15. P.S.I.) for five minutes and then for an additional five minutes at a pressure of 35 pounds per square inch, without showing indications of admitting moisture.


water-sapphire – Colorless pebbles from Ceylon (Sri Lanka); topaz, sapphire, quartz, etc., or an alternate term for cordierite.


water stone – Moonstone orthoclase and hyalite.


water worn – A term used to describe the appearance of gem pebbles which have come from alluvial deposits, in the making of which the fragments were rolled and worn so that the original outlines of the rough have been obscured or rounded. The amount of wear may be great or little depending upon many factors, such as the length of time the stone was subject to the wear, and the hardness of the material.


wax – In jewelry, a generic term applied to a family of specially formulated waxes, each for a specific purpose, e.g. casting, filing, forming, drilling, shaping, etc.


wax agate – Yellowish or yellowish-red agate with a waxy luster.


wax injector – A device for forcing molten wax into a rubber or metal mold in order to make a wax pattern. Provides pressure for the wax injection is supplied by compressed air or hydraulic pressure.


wax opal – Yellowish opal with a waxy luster.


wax pearl – A term which has been applied to the wax-filled glass beads coated with pearl essence commonly sold as inexpensive imitation pearls. The filling gives strength to the glass bead and makes it less likely to break.


wax pen – An electrically heated device used to dispense wax in making or repairing wax patterns.


web – The part of a gear wheel that connects the hub with the rim.


Webster-Whitcomb – The name of design of wire-chuck used by more makers of watchmakers’ lathes all over the world than any other. It was introduced in 1889 by Ambrose Webster and John Whitcomb of the American Watch Tool Co., of Waltham, Mass. These “W. W.” chucks are interchangeable in all makes of lathes that have adopted this design.


wecker – On clocks made in Germany or for German trade, denotes the key for winding the alarm-work.


wedding ring – A circlet of precious metal, with or without gems set in it, given to the bride, and sometimes also to the groom, as part of the wedding ceremony.


wedging – Preparation of chronometers or watches for shipment by pushing tapered pieces of cork or pith between balance-arms and plate, to prevent damage during transportation.


wegeler, wackeler – A German term for thin slices of agate with a fine structure of colorless needles, so that as they are turned light seems to shimmer back and forth as if they were water.


weld – To unite pieces of metal by heating until fused together.


well – The dark non-reflecting area in the center of a poorly-cut brilliant.


wernerite – The intermediate scapolite, containing about half and half of meionite (calcium aluminum silicate) and marialite (sodium aluminum silicate), the two end members of the scapolite series.


Wesselton – An older term in diamond color-grading between “top Wesselton” and “top crystal,” approximate to “H” in G1A system or 2 in ACS system.


Westphal’s balance – A scale using a weight and a sinker which is used for determining the specific gravity of a heavy liquid. Manufactured by a German mechanic named Westphal in Celle, Hanover, hence the name.


wet diggings – Alluvial diamond deposits, the pipes being known as dry diggings.


wheel chuck – Chuck for watchmakers’ lathe, for holding wheels or discs; a series of concentric curved steps formed on the jaw-faces afford assorted diameters to grip the work. These chucks are usually made in sets of five; more rarely in sets often.


wheel-stretcher – Tool for enlarging slightly the diameter of a watch train wheel. Most of them work on one of two different principles: 1. Two steel blocks, with flat faces opposite each other, the blocks sliding on a central pin, a wheel being embraced between them. The upper block is struck light, repeated taps with hammer while wheel is turned by a finger, compression stretching the wheel larger. 2. Two steel rollers with slightly curved faces are adjustable toward each other. Turning the rollers with a wheel between them compresses the metal and stretches and enlarges diameter of the wheel.


whern – An old English name for CHERT.


whiplash regulator – Form of regulator for watches with a curved spring surrounding the index-pointer, its outer end pressing the pointer against the end of the screw that provides a micrometric control for moving the pointer.


whitamite – Yellowish to reddish epidote.


Whitby jet – Jet from the best known locality, the Yorkshire coast, near Whitby, England.


white carnelian – Milky white chalcedony with perhaps some reddish indications of its relationship to true carnelian.


white diamond – A diamond color grade approximately equivalent to G.I.A. grades F, G, H, and A.G.S. grades 1, 2; between “river” or “finest white” and “tinted white,” “top crystal” or “commercial white.” 2. Jewelry. A fine, hard, white polishing compound.


white garnet – Grossular garnet, found in Tanzania in gem quality, rare elsewhere and not of gem quality. Because of the similarity of its trapezohedral crystals, the term had erroneously been applied to leucite, but should now be even more sedulously avoided in view of the Tanzanian finds.


white gold – Usually, an alloy of gold, copper, nickel and zinc; developed in America in the mid-1920’s, to meet the demand for a workable, lower-cost substitute for platinum; it caught on at once, outselling and largely replacing the earlier, more expensive white alloys combining as much as 19% palladium with gold.


white metal – A mixture of tin, antimony and copper in varying proportions. Sometimes used as a base for inexpensive electroplated jewelry.


white moss agate – Actually chalcedony, rather than agate for the body color is white or light-colored and translucent and is marked with whitish opaque areas, resembling the black moss more commonly seen, but coarser in texture and usually less varied and less interesting.


white-opal – One of the broad opal classifications, the other being black-opal. The body color of white-opal is always light, white, yellowish, etc. See BLACK-OPAL.


white-smoothing – A variety of gray-finish on flat steel work that is particularly light in color and “frosty” in appearance. Powdered Turkey oilstone, decanted for uniformity of grain, used on a ground-glass lap with a very light thin oil, is means of production. See DECANTATION; GRAY FINISHING.


white stone diamonds – Misnomer for imitation brilliants of any sort of white material.


whiting – Chalk or carbonate of lime, pulverized and washed, used for polishing silver, etc.; either dry or mixed with various liquids to a pasty or creamy condition.


Wicklow diamond – Misnomer for rock crystal from Wicklow, Ireland.


wig-wag – A machine, sometimes in form of a lathe attachment, for polishing steel parts. Essentially, a straight-line lap used with abrasives, and given a reciprocating motion against the work by action of a piston, connecting rod, and crank or wheel; used largely in watch factories in place of rotary-lap polishers.


wild pearl – A natural pearl, a term used to contrast with cultured (or cultivated) pearl.


willemite – (wil’lem-ite) A zinc silicate not infrequently found in the oxidized portions of zinc ore deposits, and an ore of zinc at Franklin, N.J. At this unique occurrence it is sometimes found in transparent yellow, white, green and reddish masses which have been cut by gem collectors as unusual gems. Hardness, 5 1/4 specific gravity, about 3.90; refractive index, about 1.70. It is often highly fluorescent in ultra-violet light and a synthetic willemite is an important constituent of the fluorescent linings of mercury vapor cold tube lights.


williamsite – Rich, dark, oily-looking serpentine, often with black spots. A local name given to the serpentine of a Maryland occurrence.


Willoughby’s diamondiferous ballast – A Rhodesian diamond-bearing conglomerate stratum, overlying the basal granite at Willoughby and Ngamo in the Gwelo district.


wilnite – Reported in one work to be a yellowish green to greenish white variety of calcium aluminum garnet. Probably an erroneous spelling of wiluite.


wilsonite – Reported to be a purplish red scapolite, but also a rock name. Not in general usage.


wiluite – A variety of vesuvianite, characteristically dark green in color and in short prismatic, doubly terminated crystals. It occurs near the Wilui River in Russia, and the name has, through ignorance, also been applied to a greenish grossularite which is associated with it and is sometimes cut. The vesuvianite of this occurrence has no gem value, but for some reason seems to get into most of the gem books.


winchellite – Same as LINTONITE.


winding square – 1. The square on which the winding key fits in a key-wind watch. 2. A steel square in a handle for winding stem-wind watches not in their cases, during repairs.


winding-stop – In fuzee timepieces, a device to prevent overwinding which would break the fuzee chain; consists of a hinged finger which is raised by the chain as it rises during winding, eventually getting in the way of a finger projecting from top of fuzee, which is thus prevented from being turned further by the key.


wing pearls – Flat, elongated pearls, slightly resembling a wing in outline.


wing shell – Shell of the Pinna.


wire chuck – Chuck for holding work of cylindrical form in watchmakers’ lathe. Made of one piece of steel, with three jaws on springs allowing jaws to close on work by drawing chuck into tapered lathe spindle throat with a threaded tube, on a hand-wheel, engaging thread on end of chuck. Average set contains about 35 different sizes (hole-diameters) of chucks. Also called split-chucks and collets.


wire-drawing – See DRAW-PLATE.


wire-drawing bench – A geared device for drawing wire too heavy to be drawn by hand, through drawplates.


wire gauge – A flat plate of metal, pierced with holes of graduated diameters numbered to measure sizes of wire, etc. The system used mostly in the watch trade is called Stubs steel wire gauge. There are 80 sizes in this, No. 1 the largest, .227-inch diameter, down to No. 80, .0135-inch diameter.


wire lines – The English term for braided metal cable cords for weight-driven clocks.


wire springs – A type of click or similar springs made of bent round tempered steel wire, instead of cut out flat steel; used in cheap watches and clocks.


Wisconsin pearls – Once synonymous with especially fine Unio pearls from the upper Mississippi River. They are light green, steel blue, purple, rose, red or reddish brown.


Wohlwill process – Electrolytic process for refining gold bullion, used by mints and other large refineries. Anodes of impure gold go into solution in an aqueous electrolyte containing gold chloride and hydrochloric acid, while pure gold deposits out on sheet cathodes.


wolf’s eye – Moonstone.


wolf’s eye stone – Deceptive name for tiger eye.


wolf teeth – Winding wheel teeth with curved, epicycloidal flanks on one side.


wood agate – Wood which has been replaced by jasper; petrified wood.


wood opal – Wood which has been replaced by opal; in general, this term would not be applied to precious opal even though it had originated, as did most of the Virgin Valley, Nevada, material, in this way.


Wood’s glass filter – A British ultra-violet light filter which absorbs most of the visible light and transmits the ultra-violet. Doubtless the equivalent of Coming’s Corex filters.


wood’s metal – One of a group of low-fusing metals used in making metal molds for injection of wax patterns. Melting points vary from 180°F to 240°F.


wood stone – A wood-like brown-banded jasper.


works – Colloquial term for the movement or mechanism of a watch, considered apart from the case.


World Diamond Federation – International organization of diamond exchanges, bourses or clubs, with affiliates in Amsterdam, Holland; Antwerp, Belgium (4); Idar-Oberstein, West Germany; Israel (2); Johannesburg, South Africa; London, England (2); Milan, Italy; New York, N.Y. (2); Paris, France; and Vienna, Austria. Diamond exchanges also exist in Sao Paolo, Brazil; Chiasso, Switzerland; Bombay, India; Hong Kong and other places.


world eye – Hydrophane. (Oculus mundi).


worm escapement – A watch escapement introduced in 1887 by the New York Standard Watch Co. of Jersey City, N.J., using worm-gear to drive the escape-wheel. About 12,000 watches were made with it, but the principle proved no advantage and the design was discontinued. See WORM-GEAR.


worm gear – A form of gearing used to transmit power from one arbor to another that is not parallel to the other one; usually at a right angle. Used for driving governor-fan in music boxes, in universal indexes of wheel-cutters and in several formerly-used watch escapements. In it, one arbor carries pinion leaves which engage with a screw-like thread on the other arbor.


Worshipful Company of Goldsmiths of the City of London – More formally termed Wardens and Commonality of the Mystery of Goldsmiths of the City of London; ancient trade guild established before 1180; named “guardians of the craft” by Edward I in 1300, incorporated by royal charter in 1327, and responsible ever since for the London Assay Office at Goldsmiths’ Hall near St. Paul’s Cathedral. The primary meaning of the expression “hallmark” is the mark of Goldsmiths’ Hall.


wortle – The steel plate through which a wire is drawn in order to reduce its diameter or give it a special contour.


wriggle – An ornament, sometimes called “joggled” work. It is executed with a small tool on the order of a chisel. The pattern is cut on the article by rocking or joggling the tool along.


wristlet – English trade-term. See WRIST WATCH.


wrist watch – A small watch on a bracelet or strap to be worn on the wrist. Some tradesmen distinguish such watches intended for men’s wear as “wrist” watches, and smaller watches worn by women, “bracelet” watches. Introduced about 1910, they achieved popularity during World War I.






xalostocite – An alternative name for the pink grossular of Xalostoc, Morelos, Mexico; also known as landerite and rosolite.


xanthite – A name which has been given to a yellow-brown vesuvianite from Amity, N.Y. It comes from the Greek word for yellow, but, like all such local and superfluous names, should not be used.


xanthos – A yellow brown stone of the Greeks; doubtless (since it became red on heating) it was largely limonite.


xihuitl – Mexican term for a turquoise found near the City of Mexico by the Aztecs.


x-rays – Penetrating short wave-length waves with many gem applications to interest the jeweler. They can be used to identify questionable stones and pearls, and they can be used to alter the color of various gem stones.


xyloid jasper – Petrified wood.


xylopal – A fancy name for opalized wood.






yachting timer – Long hand completes one turn in 60 seconds. The 15-minute register for the small hand has three differently colored, 5-minute segments to indicate “warning,” “preparatory” and “start.”


YAG – Shorthand for yttrium aluminum garnet.


yanolite – Violet axinite.


year mark – A character or symbol stamped on articles of silver or gold by British gold and silversmiths to mark the year in which the article was manufactured. One of the four or more marks or symbols making up the hall mark.


yellow carneol or carnelian – Chalcedony with an iron stain, more yellow than red.


yellow diamond – A color-grading term measured by grade Z on the GIA scale or grade 10 on the ACS scale. Diamonds that are lighter than Z or 10 are graded faint, very light or light yellow, depending upon depth of hue. Stones that are deeper than Z or 10 are designated fancy yellow.


yellow gold – The most popular gold alloy. An alloy of gold, silver, copper and sometimes, zinc.


yellow ground – The oxidized upper portion of the diamond pipes; with depths, oxidation ends and the matrix rock becomes blue ground.


yellow ochre – An earth or loam, in washed powder form, used by jewelers, mixed with water, to paint on work at places where solder is not wanted to flow. See LOAM, OCHRE.


yellow orthoclase – A transparent yellow variety of orthoclase found in Madagascar, often in large pieces and sometimes cut for gem purposes.


yielding-attachment – Type of fastening for outer end of mainspring in which there is a pivoting effect at the outer end of spring, like the “T-end;” or the device of a short separate piece of spring set between the barrel hook and the spring-end.


yoke – 1. The part in a lever-set watch that carries gear-wheels for shifting from winding to setting by the stem; the rocking-bar, or vibrating arm. 2. The part of the pallets in lever escapement that holds the pallet stones.


Yowah nuts – Small ferruginous boulders from Yowah station, 27 miles northwest of Eulo in western Queensland. Generally of walnut or almond size, 7 to 10 per cent contain opal as the center or as a thin band around an ironstone center.


yii – Chinese word for jade, but also applied to any of the better stones like jade which are carved and used in that fashion. Hence, it may also refer to aventurine, californite, etc.


yttrium aluminum garnet – Misnomer for the synthetically grown (using the word synthetic in its broadest sense) compound of yttrium and alumina. It crystallizes in the cubic system, like magnesium aluminate (spinel) with a high refractive index 1.833, a hardness of 8/4, density of 4.5 and a dispersion of .028. While the internal structure is like that of a garnet, it is not a silicate and to call it a garnet is a misnomer that could lead to misunderstandings. Its counterpart has not been found in nature, so it is not a true synthetic in the original sense of the term as applied to gemology. It has many names in trade promotions, including DIAMANITE, DIAMONAIR, DIAMONDLITE, DIAMONIQUE, DIAMONTE, Dl’YAG, LINDE SIMULATED DIAMOND, and TRIAMOND.






Zabeltitzter diamonds – Easy to guess that this is a misnomer for rock crystal.


Zanzibar copal – An ancient fossil gum found in desert sands (gum animi).


zeasite – Wood opal and an old name for fire opal.


Zener diode – A diode that breaks down and allows all current to go through, when an increase of voltage is forced to it; then again becomes normal.


zeolites – A group of closely related hydrous silicates of sodium, calcium, aluminum, etc. They commonly occur in association with basaltic rocks and apparently form at a late stage as rock solidifies. Some of them are of gem interest, lintonite, thomsonite, pectolite, etc. Artificial zeolites are used as water softeners because of their property of taking calcium in place of sodium.


zeuxite – A green Brazilian tourmaline, also called TALTALITE or BRAZILIAN EMERALDS.


zinc – A bluish-white metal; melting point, 787°F; malleable only between 230°F and 410°F; at other temperatures it is brittle. The jeweler will encounter it chiefly in brass, hard solder and as an alloy in karat gold. During the melting and pouring of alloying, zinc absorbs oxygen and prevents the oxidation of silver or copper. A zinc content up to 14% does not affect the physical properties of gold, except to make it paler. But above 14% it makes gold reddish and brittle. It cannot be used if the gold is to be enameled.


zinc-aluminum – An alloy used in the making of die castings. See DIE CASTING.


zinc blende – Sphalerite.


zinc chloride – A saturated solution of zinc in hydrochloric acid, the most largely used flux for soldering metals with lead-tin alloys. See SOLDERING.


zinc compensation – A pendulum with cylindrical tube or bob resting on a platform supported by the pendulum rod, designed to effect a compensation for the varying lengths of the rod in changes of temperature.


zinc spinel – Gahnite.


zinc-white – Zinc oxide; a white paint in cake form, soluble in water, for preparing a surface on metal goods on which designs are drawn for engraving.


Zircolite – A trade-name for synthetic colorless sapphire.


zircon – An important gem stone, a zirconium silicate. It is characterized by very high refractive indices, about 1.93 and 1.99. Hardness, 7 1/4-7 1/2; specific gravity, 4.68. It has high dispersion and well-cut stones have a good fire. The natural colors are yellow, brown, red and green. Heat creates blue, colorless and greenish stones. Alternative names include hyacinth, jacinth and jargoon. Bad and misleading names include Matura diamond, Siam aquamarine, etc.


zircon cut – A modified brilliant cut in which the culet is replaced by 8 extra triangular facets.


zircon spinel – A misleading term for synthetic, pale blue spinel.


zirctone – Another undesirable trade-name for synthetic bluish-green sapphire.


zmilampis or zmilaces – Grecian term for cat’s-eye but doubtless referring to an asbestos fiber filled quartz, with which the true cat’s-eye was confused until a much later date.


zodiac stones – Stones ascribed to the 12 signs of the zodiac, an imaginary belt in the heavens through which the sun, moon and planets were thought to pass, according to the belief of Babylonian and Roman astrologers.


zoisite – (zo’iss-ite) A hydrous calcium aluminum silicate, closely related to epidote. Commonly grayish and of no gem interest prior to the discovery of tanzanite. A very attractive pink massive variety, known as thulite, from its occurrence in Norway (ancient Thule), is sometimes cut into decorative objects. Refractive index, about 1.70; specific gravity, 3.12; hardness, 6-61/z. See TANZANITE.


zoning – Changes in color or refractive index revealed on examination of a stone that indicate a change of growing conditions during its growth. They are helpful in showing whether a crystal grew as a crystal, with straight lines and angles, or if it grew as a boule, with curving lines. Only useful in the case of Verneuil-type synthetic crystal growth; crystals like emerald, flux fusion rubies and alexandrites grow as crystals with straight line variations or zoning, and hence do not reveal synthetic origin in this way.


zonite – Local Arizona name for a color chert or jasper.


zonochlorite – (zo-no-klor’ite) A chlorastrolite-like amygdular fibrous green-banded pebble from Lake Superior.


Zubara emeralds – Emeralds from the ancient Egyptian emerald mines under Mount Zubara, near the Red Sea.