19 Photos
Colemanite
Chemical Formula	CaB3O4(OH)3·H2O
Species	Borates
Crystal System	Monoclinic
Mohs Scale	4
Specific Gravity	2.42
Color	Colorless, white, yellowish, grey
Streak	White
Luster	Adamantine, Vitreous
Refractive Index	n = 1.586 n = 1.592 n = 1.614
Diaphaneity	Transparent, Translucent
Cleavage	PerfectOn perfect; on distinct.
Fracture	Irregular/Uneven, Sub-Conchoidal
Crystal Habit：Massive granular to coarsely crystalline, most commonly nodular.
Geological Setting：Borate deposits formed in arid alkalai lacustrine environments.

Colemanite (CaB₃O₄(OH)₃·H₂O) is a borate mineral found in evaporite deposits of alkaline lacustrine environments. Colemanite is a secondary mineral that forms by alteration of borax and ulexite.

It was first described in 1884 for an occurrence near Furnace Creek in Death Valley and was named after William Tell Coleman (1824–1893), owner of the mine Harmony Borax Works where it was first found. At the time, Coleman had alternatively proposed the name "smithite" instead after his business associate Francis Marion Smith.