Colemanite
Image: Aangelo (CC BY-SA 3.0)
Mineral NameColemanite
Chemical FormulaCaB3O4(OH)3·H2O
Mohs Hardness4.5
Crystal Systemmonoclinic
Lustervitreous
Streak Colorwhite
CleavagePerfect on {010}, good on {001}, distinct on {100}
Fractureuneven
Specific Gravity2.42
Colorscolorless, white, yellowish, grayish
Transparencytransparent
Type LocalityBoron, California, USA; Death Valley, California, USA; Bigadiç, Turkey
Mineral GroupBorates
Usesboron source, fiberglass production, ceramics, detergents, agriculture, collector
Associated Mineralsborax, ulexite, gypsum, calcite, celestine, sulfur
Rarityuncommon
Description
This specimen of Colemanite displays a strong green fluorescence under long-wave UV light, indicating its characteristic luminescent properties. In natural light, it typically appears as colorless to white, often forming blocky or prismatic crystals.
Geological Context
Colemanite is a secondary borate mineral that forms in evaporite deposits, particularly in arid lacustrine environments where boron-rich waters evaporate. It is often found in association with other borate minerals in ancient lake beds.
