Table-cut: See Emerald Cut.
Tantalum: A rare, very hard, heavy, gray metallic element that is exceptionally resistant to corrosion and chemical attack below 150°C. It is used to make light-bulb filaments, electrolytic capacitors, lightning arresters, nuclear reactor parts, and some surgical instruments.
Tanzanite: A variety of zoisite named after its country of origin, Tanzania, where it was first discovered in 1967 and is still the only place where it can be found. Tanzanite is popular for its brilliance and is known for its varying shades of violet; from deep rich purple to lilac. The gem can be heated to achieve the most sought after shade, a vibrant blue violet. Good quality tanzanite is usually faceted, but the rare pieces that have flaws are simply made into cabochons.
Tarnish: A dulled luster or finish caused by a thin deposit of a dirt which discolors the surface of metal and is easily removed. Also a reaction between metals and other chemicals which discolors the surface, particularly silver which reacts with sulfur. The silver sulfide can be removed with a proprietary cleaning product and gentle abrasion.
Taxco: (TAHKS' coh) The center of silversmithing in Mexico. Silver produced there up until about 1970 is considered collectible. In 1979 the government began to require silversmiths to stamp a registration mark consisting of two letters and several numbers.
Tea caddy: A decorative box created for storing tea leaves. Many have two compartments; one for black tea and the other for green tea. Some of the finest tea caddies were created in England and crafted of exotic woods adorned with tortoise shell, ivory and mother of pearl.
Tiffany Setting: A generally round, high, six-prong setting with long, slender prongs that flare out from the base introduced by Tiffany & Co. in 1886. It is most commonly used today for large stones such as a diamond solitaire.
Tiger's Eye: A semiprecious variety of quartz found in South Africa. It may be yellowish-brown, bluish, or red in color with bands of darker and lighter shades across its surface. It has a silky luster, and catches the light causing the chatoyant quality.
Tin: A malleable, silvery metallic element which is not easily oxidized in the air, and so is used chiefly to coat iron to protect it from rusting. It is primarily extracted from the ore cassiterite where it is found as an oxide. Tin is malleable at ordinary temperatures, but brittle when heated and is a part of numerous alloys such as soft solder, pewter, type metal, and bronze. It is most commonly used in the form of tin foil with mercury to form the reflective surface of mirrors.
Toe Ring: A type of body jewelry worn around one or more toes. Toe rings come in styles similar to rings worn on the fingers, but toe rings have a small gap on the bottom of the ring to allow them to slip over the tips of the toe more easily.
Toggle clasp: A means of fastening two ends of a chain together consisting of a ring on one end and a short bar on the other. The bar is slid through the ring and sits across it so it does not slide or pull.
Tongue Bar: A bar shaped stud worn through a hole pierced in the tongue.
Topaz: A fluosilicate of aluminum that occurs in rhombohedral crystals and is used as a gemstone. Although it is a hard stone, topaz can be susceptible to breaking. According to some, the name is from Topazos, a small island in the Red Sea, where the Romans obtained a stone which they called by this name, but which is now called chrysolite. Topaz is sought after because it is lustrous, has double refraction and a strong hue. It may be found in many colors, such as blue, brown, clear, green, orange, pink, red, yellow, white. The most valuable topaz is "Imperial" topaz with a golden yellow to orange color. The most popular color is an enhanced blue treated with heat to develop it into a rich “Tiffany” blue color which resembles aquamarine, but is more affordable. (see blue topaz rings )Yellow quartz is sometimes called topaz, but is considered "false topaz". True topaz is said to be the symbol of love and affection to act as a protector by making the wearer invisible in emergencies. Topaz is the birthstone for November.
Tortoise Shell: A mottled, nutty brown shell material with a spotted, striped, or sometimes even speckled pattern. Popular for 19th century jewelry and hair combs, tortoise shell was banned and is no longer used for these items. There are very close plastic imitations of tortoiseshell. One technique to differentiate tortoise from its imitators is to touch the surface with a hot pinpoint. Tortoise will give off a smell like burning hair, while plastic will emit an acrid chemical odor.
Total Depth Percentage: A measure of the depth of a diamond from the table to the culet divided by the average diameter, (width), of the girdle. The depth percentage of most diamonds is between 53 and 63 percent.
Tourmaline: A complex crystalline silicate occurring usually in three-sided or six-sided prisms terminated by rhombohedral or scalenohedral planes containing aluminum, boron, and other elements. Black tourmaline (schorl) is the most common variety, but there are also other varieties, as the blue (indicolite), red (rubellite), also green, brown, and white. The red and green varieties when transparent are valued as gems. Tourmaline can be found in more colors than any other stone and heat can also be applied to tourmalines to lighten, or enhance, the existing hue of the gem.
Translucent: Allowing light to pass through, but not transparent.
Transvaal jade: See African Jade.
Treated Turquoise: A process by which the pores of the turquoise stone are filled with a transparent substance such as mineral oil, paraffin wax, or plastic to improve the color and make it more desirable.
Tremolite: A white or pale green mineral of the amphibole group composed of calcium magnesium silicate and used as a form of asbestos. The compact variety of tremolite, called nephrite, is a form of jade.
Triangle cut: See Trillion-cut.
Trilliant: See Trillion-cut.
Troy Weight: gold and silver are measured in "Troy weight", from Troyes in France, a system that includes pennyweights, ounces and pounds. The ounces and pounds do not equal the Avoirdupois or customary U.S. system that other common goods are measured in. gold is also commonly measured in metric grams. A pennyweight (abbreviated dwt.) is equal to 1.5552 grams.
24 grains = 1 pennyweight = 1.5552 grams
20 pennyweight = 1 troy ounce = 31.1035 grams
12 ounces = 1 pound troy = 373.24 grams.
Tsavorite: A transparent green garnet of the grossular family of garnets found at Tsavo, Kenya. Tsavorite is not the only green garnet, see also Uvarovite.
Turquoise: A hydrous aluminum phosphate colored by copper salts found in desert regions throughout the world and used in jewelry by the natives who live there including Mongolian, Chinese, Native Australian, Persian, and Southwestern Native American. Different colors of turquoise, varying from sky blue to nearly green occur in untreated turquoise. Turquoise Ring: Brown or grey streaks in turquoise are caused by the "matrix", or "mother stone", from which the turquoise is mined. Interesting matrix patterns are considered to add beauty to the stone. Only Persian turquoise is usually without apparent matrix. Modern turquoise stones that appear very shiny and absolutely flawless are actually manufactured. Pulverized turquoise is reconstituted with a plastic binding medium then cut and shaped as though it were natural stone. This material is generally avoided by collectors. Touching the stone leaves oils on it which alters the color of the turquoise over many years. Collectors tend to value these color nuances as "the patina of time". This unique stone is usually cut into cabochons, or domes, to enhance the natural beauty of the gem. Turquoise is considered a source of good fortune and beauty.
Turquoise, Treated: A process by which the pores of the turquoise stone are filled with a transparent substance such as mineral oil, paraffin wax, or plastic to improve the color and make it more desirable.