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Last updated on April 19, 2014 at 18:42 EDT

Crystallography Reference Libraries

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Amphibole
2005-05-26 12:19:41

Amphibole defines an important group of dark-colored rock-forming inosilicate minerals composed of double chain SiO4 tetrahedra linked at the vertices and generally containing ions of iron and/ or magnesium in their structures. In chemical composition and general characteristics they are very similar to the pyroxenes and, like them, fall into three series according to their system of...

Aragonite
2005-05-26 12:17:18

Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. Its structure differs from calcite and leads to a different crystal shape, an orthorhombic system with acicular crystals. By repeated twinning pseudo-hexagonal forms result. It may be columnar or fibrous, occasionally in branching stalactitic forms called flos-ferri (flowers of iron) from their...

Kyanite
2005-05-26 09:41:33

The mineral kyanite is an aluminium silicate of the sillimanite group (along with andalusite and sillimanite), also called alumino-silicate. It has the formula Al2O3·SiO2 (Al2SiO5). Its hardness varies widely depending on its crystallographic direction, from 5 to 7.5, and it has a specific gravity of 3.56-3.67. It is translucent, usually blue, but possibly white, gray, green, or black. It...

Limonite
2005-05-26 09:37:09

Limonite Limonite is a ferric hydrate of varying composition, the generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as Limonite often contains a varying amount of oxide compared to hydroxide. Together with hematite, it is mined as ore for the production of iron. Limonite is heavy and yellowish-brown. It is not a true mineral, however, but a...