Stichtite is a mineral, a carbonate of chromium and magnesium.
Star sapphire is a type of sapphire that displays asterism, a star-like optical effect.
Stolzite is a rare mineral; much rarer than wulfenite and usually occurs in very minute crystals.
Strontianite is a rare pale greenish-yellow or white mineral consisting of strontium carbonate.
Sugilite is a rare mineral named after Ken-ichi Sugi, a Japanese geologist who first discovered the material in 1944 on the Japanese island Shikoku.
Sunstone is a reddish variety of oligoclase feldspar, used as a gem, having a red and bright-yellow play of color.
Taaffeite is a rare mineral BeMgAl4O16 consisting of oxide of beryllium, magnesium, and aluminum and resembling mauve-colored spinel.
Talc is a white, grey, or pale green soft mineral with a greasy feel, occurring as translucent masses or laminae and consisting of hydrated magnesium silicate.
Tantalite is a rare, dense, black mineral consisting of a mixed oxide of tantalum, of which it is the principal source, and iron.
Tanzanite is the blue and violet variety of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate), caused by small amounts of vanadium.
Tektites are small black glassy objects, many of which are found over certain areas of the earth's surface, believed to have been formed as molten debris in meteorite impacts and scattered widely through the air.
Tephroite is a mineral Mn2SiO4 consists of Manganese silicate and is isomorphous with olivine.
Thaumasite is a white mineral consisting of a basic silicate, carbonate, and sulfate of calcium
Thomsonite is a mineral of the zeolite family consisting of a hydrous silicate of aluminum, calcium and sodium.
Tiger's Eye is a yellowish-brown semiprecious variety of quartz with a silky or chatoyant luster, formed by replacement of crocidolite with chalcedony.
Topaz is a precious stone, typically colorless, yellow, or pale blue, consisting of a fluorine-containing aluminum silicate.
Tourmaline is a typically black or blackish mineral that occurs as prismatic crystals in granitic and other rocks.
Tremolite is a white to gray amphibole mineral that is characteristic of metamorphosed dolomitic limestones.
Triphylite is a mineral, a rare phosphate of lithium, iron, and manganese, usually occurring in masses of a bluish or greenish color.
Tsavorite os a green variety of grossularite, found in Kenya in 1975 and used as a gem.
Tugtupite is a sodium aluminum beryllium silicate first discovered in 1962 in Greenland.
Turquoise is a semiprecious stone, typically opaque and of a greenish-blue or sky-blue color, consisting of a hydrated hydroxyl phosphate of copper and aluminum.
Ulexite is a mineral occurring on alkali flats as rounded masses of small white crystals.
Uvarovite garnet is one of the rarest members of the garnet family. Usually only seen as druzy on matrix, these crystals are seldom faceted.
Vanadinite is a rare reddish-brown mineral consisting of a vanadate and chloride of lead, typically occurring as an oxidation product of lead ores.
Variscite is a bluish to greenish gem mineral sometimes confused with or substituted for turquoise —called also utahlite
Väyrynenite is a very rare mineral. Crystals as well as faceted gemstones in reddish, pinkish, and orange colors are prized collector’s items.
Villiaumite is a a mineral consisting of a sodium fluoride. Despite their small size, they are desirable because so few stones exist.
Vivianite is so fragile and soft, any faceted gems would be difficult to handle safely, let alone wear. Nevertheless, its blue and green colors are so rich, a few stones (very few) have been cut.
Wardite is another of the many phosphates that have been cut by collectors. It is pale colored and not terribly attractive and is fairly soft and fragile. It is seen far more frequently as cabochons than as faceted stones.
Wavellite is a very attractive mineral, well-known to collectors. Its radial aggregate crystal clusters can be cut into extremely interesting stones.
A rare triclinic carbonate mineral, usually white, lemon yellow, or amber, and sometimes translucent.
Whewellite is a mineral consisting of calcium oxalate occurring in colorless or white monoclinic crystals
Wilkeite is a mineral consisting of an hydroxylapatite in which phosphorous is partly replaced by carbon, sulfur, silicon, or a combination thereof
Willemite is a mineral of varying color consisting of a silicate of zinc and occurring especially in massive or granular forms.
Witherite is a translucent white or gray orthorhombic mineral consisting of a carbonate of barium
Wollastonite is a triclinic mineral consisting of a native calcium silicate occurring usually in cleavable masses.
Wilfenite is a tetragonal mineral that is a complex oxide of lead and molybdenum and occurs especially in bright orange-yellow tabular crystals.
Xonotlite is a mineral that is a hydrous calcium silicate.
Yugawaralite is a very rare colorless to pinkish zeolite mineral.
The mineral zektzerite is a member of the tuhualite group and was first found in 1966 by Seattle mineralogist Benjamin Bartlett.
Zincite is a very rare mineral, essentially restricted to one important locality. Well, terminated crystals were found only up to about 3-4 inches, but larger masses, weighing several pounds, have been encountered in the ore bodies.
Zircon is a mineral occurring as prismatic crystals, typically brown but sometimes in translucent varieties.
Zunyite is a fluorosilicate mineral of alumina occurring in tetrahedral crystals.