Top Results for Silicate

Euclase is a rare beryllium aluminum silicate mineral with the chemical formula BeAlSiO₄(OH). Its name derives from the Greek words "eu" (good) and "klasis" (breakage), referring to its perfect cleavage. The mineral typically forms prismatic crystals in granitic pegmatites and hydrothermal veins, wi...

Phenakite, also spelled phenacite, is a beryllium silicate mineral with the chemical formula Be2SiO4. It commonly forms transparent, colorless crystals but may also appear pale yellow, pink, or brown, and its hardness and relatively high refractive index allow suitable specimens to be cut as gemston...

Idocrase is the traditional name for vesuvianite, a calcium aluminum silicate mineral that commonly forms in skarn and other rocks altered by contact with igneous bodies. It occurs in colors including green, brown, yellow, and blue, and crystals generally have a tetragonal form. Abraham Gottlob Wern...

Willemite is a zinc silicate mineral with the chemical formula Zn2SiO4 and a minor source of zinc ore. It occurs in several colors and forms, but specimens from the Franklin and Sterling Hill zinc deposits in New Jersey are especially associated with bright green fluorescence under shortwave ultravi...

Sillimanite is an aluminium silicate mineral with the chemical formula Al2SiO5, and one of three polymorphs that also include andalusite and kyanite. It forms mainly in metamorphic rocks exposed to high temperatures and is also known as fibrolite when it occurs in fibrous aggregates. Transparent or...

Neptunite is an approved silicate mineral with the formula KNa2LiFe2+2Ti2Si8O24. It commonly forms black to dark-red monoclinic crystals and is associated with alkaline pegmatites; its type locality is the Narsaarsuk pegmatite in Greenland, where it was first published in 1893. In California it is n...

Scapolite cat's eye is a chatoyant gemstone variety belonging to the scapolite mineral group. Its narrow, moving band of reflected light is produced by aligned internal inclusions or structures, an optical effect known as chatoyancy. The material is relatively uncommon in fine gem quality and is ass...

Andalusite is an aluminum silicate mineral with the chemical formula Al2SiO5. It forms in metamorphic rocks and is named after Andalusia in southern Spain. Gem-quality andalusite is valued for pleochroism, meaning that its apparent color changes when viewed from different directions. A related varie...

Zircon is a naturally occurring mineral composed mainly of zirconium silicate, with the chemical formula ZrSiO4. It crystallizes in the tetragonal system and commonly forms durable crystals in igneous rocks, metamorphic rocks, and sedimentary deposits. Transparent varieties can be cut as gemstones a...

Neptunite is a sodium, lithium, iron, titanium, and silicate mineral known especially from San Benito County, California. It commonly occurs as dark red to black crystals and is associated with other unusual minerals in its principal Californian locality. Some specimens show chatoyancy, a reflective...

Scapolite is a group of closely related aluminosilicate minerals that commonly forms in metamorphic rocks and in some altered igneous environments. Its colors range from white and gray to yellow, violet, pink, and blue, and some transparent crystals are cut as gemstones. Scapolite may also display c...

Charoite is a rare purple silicate mineral and rock material known for swirling, fibrous patterns in shades of violet, lavender, lilac, black, and white. It is found in the area of the Chara River in the Sakha Republic of eastern Russia, which is its principal known source. Charoite is usually cut i...

Pumpellyite is a group of calcium, magnesium, aluminum, iron, and manganese silicate minerals formed mainly during low-grade metamorphism. It commonly occurs in altered volcanic rocks, especially where rocks have been affected by pressure, heat, and circulating fluids at relatively low temperatures....

Kyanite is an aluminosilicate mineral with the chemical formula Al2SiO5. It is distinguished by strong directional variation in hardness: its hardness differs depending on whether a specimen is tested parallel or perpendicular to its crystal structure. Kyanite commonly occurs in blue, although other...

Dumortierite is a fibrous aluminum borosilicate mineral that commonly forms columnar crystals or parallel aggregates. It was first described in 1881 from France and named for the French paleontologist Eugène Dumortier. Its colors include bright blue, greenish blue, violet, purple, red-violet, and br...

Epidote is a calcium-aluminum-iron sorosilicate mineral with a monoclinic crystal structure and a composition commonly written as Ca2(Al,Fe)3(SiO4)(Si2O7)O(OH). It forms in a range of igneous and metamorphic rocks, as granular masses and prismatic crystals. Its characteristic colors run from pistach...

Ekanite is a rare thorium-bearing calcium silicate mineral with the ideal formula Ca2ThSi8O20. It was first found in the Ratnapura area of Sri Lanka and is named for Sri Lankan gemmologist Francis Leo Danvil Ekanayake. Ekanite is usually green but can also be straw-yellow, dark red, or colorless, an...

Prehnite is an orthorhombic calcium aluminosilicate mineral with the formula Ca2Al2Si3O10(OH)2. It was described in 1788 from the Karoo dolerites near Cradock in South Africa and named for Hendrik von Prehn, a Dutch colonial officer credited with bringing specimens to Europe. Pale green material is...