All About Jewels: Illustrated Dictionary of Jewelry

TABASHEER OPAL Tabasheer (also spelled tabashir) or pearl opal is an organic stone that forms in damaged joints (nodes) of bamboo plants. This hydrated form of silica appears as a rounded mass of opal, and looks like seed pearls.

TABLE The table is the large, flat area at the top of a cut gemstone.

TAHITIAN PEARL Tahitian pearls (also called black pearls) are dark-colored pearls. They are produced by the large, black-lipped pearl oyster Pinctada margaritifera (also called the Tahitian black pearl oyster), a mollusk found in the tropical Indo-Pacific Ocean. Black pearls come in many colors, including many body shades and overtone tints including gray (light gray to almost black), peacock green (especially valuable), aubergine (eggplant), and deep brown. The color of the dark nacre is determined by the minerals in the oyster's diet (plankton) and in its environment. Many "black pearls" are dyed or irridiated to enhance or change their color; it is difficult to tell a natural pearl from a treated pearl. Tahitian pearls are graded on six factors: 1.Shape (round is most valued), 2.Size (the larger the better), 3.Surface Quality (clean is superior to blemished), 4.Luster (the more high-gloss luster the better), 5.Nacre Thickness (thicker is better and longer lasting), and 6.Color (overtones atop the body color add value to the pearl; the most sought-after color is peacock green and darker colors are more valuable - overtone colors include blue, pink, gold, silver, aubergine, and peacock green).

TANVORITE Tanvorite is a trademarked name for a manmade gemstone. This synthetic stone is a deep blue-purple stone that resembles tanzanite.

TANZANITE Tanzanite (strontium-rich Calcium-aluminum silicate) is a valuable, transparent, blue-violet type of zoisite resembling sapphire. Tanzanite has a hardness of 6 and a specific gravity of 3.35. It is often heat-treated in order to produce a deeper blue-violet color. This mineral was discovered in 1967 by Manuel d'Souza (an Indian tailor) southwest of Mt. Kilimanjaro in Tanzania, Africa. Tanzanite is one of December's birthstones.

THERMOSET PLASTIC Thermoset plastic (also known as thermoplastic) is a hard, non-rigid synthetic substance that cannot be melted by reheating. Thermoset plastic is formed under high heat or pressure by a process known as polycondensation. Bakelite is a thermoset plastic. The bangle above is "butterscotch" bakelite.

TIE BAR A tie bar is a piece of men's jewelry used to secure a necktie. A tie bar usually has a decorative, bar-shaped front, and a clip on the back that grasps the two parts of the tie.

TIE TACK A tie tack is a piece of men's jewelry used to secure a necktie. A tie tack has a decorative front, and a pin on the back that goes through both layers of the tie. Attached to the reverse of the pin is a chain with a bar that is meant to go throught a buttonhole to secure the tie loosely to the shirt.

TIFFANY SETTING The Tiffany setting is a ring with a high, six-pronged solitaire diamond on a simple circular band. This design was introduced by Tiffany & Co. in 1886.

TIGER'S EYE Tiger's eye is a yellowish-brown to reddish-brown gemstone that has a silky luster. This gemstone has bands of yellow and brown; when viewed from the opposite direction, the colors are reversed. Tiger's eye is usually highly polished and set as a cabochon (or cut as a bead) to display the stone's chatoyancy (light reflected in thin bands within the stone). Tiger's eye is a type of chatoyant quartz with fibrous inclusions (especially crocidolite). This stone is sometimes heat-treated. Tiger's eye has a hardness of 7.0. Most tiger's eye is mined in South Africa, but it is also found in Australia, Brazil, Burma (Myanmar), India, Namibia, Sri Lanka (Ceylon), and the USA. Green-grey varieties of this stones are called cat's-eye quartz. Blue-grey to bluish varieties are called hawk's-eye. Deep brown varieties of this stone are called bull's-eye or ox-eye.

TOGGLE CLASP A toggle clasp (also called a bar and ring clasp) is a jewelry fastener in which a bar can be inserted into a ring to fasten a piece of jewelry. It is used to attach the two ends of a necklace or bracelet.

TOPAZ Topaz (aluminum silicate fluoride hydroxide) is a very hard gemstone that ranges in color from brown, to yellow to blue to pink. Pink topaz is usually created by irradiating common yellow topaz. Other colors are often created by heat-treating and/or irradiating topaz. Imperial topaz is golden orange-yellow topaz; it is the most valuable topaz Topaz has a hardness of 8 and a specific gravity of 3.5-3.6. Topaz may have been named for the legendary Topasos Island in the Red Sea.

TORQUE A torque (also spelled torc) is a necklace that consists of a narrow, twisted band made of metal. This type of ornament was worn by the ancient Celts, Britons, and Gauls.

TOURMALINATED QUARTZ Tourmalinated quartz is a variety of transparent quartz that has needle-like inclusions of black to dark green tourmaline crystals. This beautiful stone is found worldwide. Tourmalinated quartz has a hardness of 7.0. This stone is not enhanced.

TRANSLUCENT Translucent materials allow light to pass through them, but the light is diffused (scattered). Some translucent stones include moonstones, opals, and carnelian. Lucite and other plastics can also be translucent.

TRANSPARENT Transparent materials allow light to pass through them without diffusing (scattering) the light. Some translucent stones include diamond, zircon, emerald, rock crystal, and ruby. Plastics like lucite can also be transparent. In the confetti lucite bangle above, the glitter within the lucite is visible.

TREMBLER A trembler is a piece of jewelry that has a part (or parts) set on a spring; the spring-set parts move as the wearer of the jewelry moves.

TRIFARI Trifari is a pre-eminent jewelry manufacturing company that produces high-quality and beautifully-designed pieces. The company began as Trifari and Trifari in 1910, founded by Gustavo Trifari and his uncle; a few years later, his uncle left and the company was simply Trifari. Leo Krussman joined Trifari in 1917. In 1918, when Carl Fishel joined the company, they renamed the company Trifari, Krussman and Fishel (their hallmark was T.F.K.). Alfred Philippe, who had been a jewelry designer for Cartier and Van Cleef & Arpels, designed pieces for Trifari for many years. Some other Trifari designers included Jean Paris (1958 -1965), Lucius Passavanti (from about 1955 to 1968), Andre Boeut (1967 - 1979), and Diane Love (1971 - 1974). Trifari was owned by the Hallmark Company from 1975-1988, and by Crystal Brands from 1988-1994. It was then part of the Chase Capital division of the Monet Group, which later went bankrupt and was bought by Liz Claiborne (2000). The classic pin and earrings set above has paste rubies, emeralds, sapphires, and diamonds (and was designed by Alfred Philippe, about 1947-8).

TRILLION CUT The trillion cut is a triangular cut based upon a brilliant style cut (and not a stepped facet). The corners of the triangle are truncated (cut short) and there are a variety of facets, giving this cut a sparkling billiance.

TURQUOISE Turquoise is a non-translucent, porous semi-precious stone (it is a hydrated phosphate of copper and aluminum) that is usually cut as a cabochon. Turquoise was believed to have been first found in Turkey, hence its name (Turquie is the French word for Turkey). The oldest turquoise mines are located in Alimersai Mountain in Persia (Iran) and in the Sinai Peninsula in Egypt. Turquoise is found in desert regions worldwide. The finest turquoise is Persian (Iranian) turquoise; it is robin's egg blue and has no matrix (streaks of the mother stone from which they were found). North American turquoise is greener and has a matrix streaks. Over the years, oil from your skin is absorbed by the stone and it will change color slightly. Turquoise has a hardness of 6 and a specific gravity of 2.60-2.85. Turquoise is the national gemstone of Iran. Turquoise is one of December's birthstones

TWINNING Twinning is a common error in crystalization in which two crystals grow out of one another or next to one another, and their crystal lattice is oriented differently from one another (some twins are like a mirror image of each other). If the crystals have grown into one another, they are called penetrant twins (forming a cross-shape like Staurolite, a star-shape like Muscovite, and other unusual shapes). If the crystals are mirror images that grow next to one another, they are called contact twins (they are often likened to Siamese twins). Twinning can drastically change the outward symmetry of the mineral specimen, by either increasing or decreasing the symmetry (like with spinel). For example, twinning can make an orthorhombic crystal appear to be hexagonal (as in Aragonite).

All About Jewels: Illustrated Dictionary of Jewelry

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