Colemanite

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colemanite

[′kōl·mə‚nīt]
(mineralogy)
Ca2B6O11·5H2O A colorless or white hydrated borate mineral that crystallizes in the monoclinic system and occurs in massive crystals or as nodules in clay.

Colemanite

 

(named for W. T. Coleman, 1824–93, the owner of the mine where it was discovered), a mineral of the class of borates. In terms of chemical composition it is a hydrous calcium borate, Ca[B2BO4(OH)3].H2O. Complex chains composed of B(O, OH)4 tetrahedrons and BO3 triangles bonded into a three-dimensional structure through Ca2+ ions and H2O buffer molecules are present in the crystal structure. Colemanite crystallizes in a monoclinic system, forming short, colorless crystals of columnar or dipyramidal appearance, as well as continuous fine-grained masses. Hardness on the mineralogical scale, 4–4.5; density, 2,440–2,450 kg/m3.

Colemanite is formed by precipitation, along with other borates (hydroboracite, inyoite, and borax), gypsum, and clayey deposits, from boron-containing brines of continental lakes. It is also found in the deposits of hot springs. Along with the other borates, colemanite is used as a boron ore.