Colemanite (Ca₂B₆O₁₁·5H₂O) is a hydrated calcium borate forming in arid playa evaporite deposits. Named after William T. Coleman who founded the Death Valley borate mining industry, Colemanite is one of the principal calcium borate ore minerals. Death Valley (California) and Bigadiç (Turkey) supply major specimens.
Key Facts
- Mohs hardness 4–4.5.
- Monoclinic; equant, tabular, and prismatic crystals.
- Glassy clear to white color, sometimes with iridescent surface.
- Forms in arid playa evaporites alongside borax, kernite, ulexite.
- Major industrial Ca borate source for boron chemistry.
Notable Localities
Death Valley (California, USA) and Bigadiç (Turkey) are major industrial sources. Boron region (California) supplies collector specimens.
Found at these Localities
- Boron / Death Valley Borate District (波伦/死亡谷硼酸盐矿)
- Searles Lake (瑟尔斯湖蒸发岩)
