Mineral Species: Colemanite

Chemical Formula: Ca2B6O11.5H2O

Chemical Name: Hydrous Calcium

Mineral Class: Borate

Mineral Notes: Colemanite is ususally found with Borax in large lake deposits in dry regions, for example the California Playa lakes and other evapourite deposits. It is ususally white and characterised by a brilliant luster. The structure of Colemanite contains endless chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons with calcium, water and extra hydroxides interspersed between the chains.

Description: Numerous, well-formed, muli-faceted crystals of Colemanite on matrix. The mineral has a yellow tinge and a very bright glassy luster, especially on the faces of the largest crystals.

Location: Borax Pit 14, Boron, California, USA