Colemanite
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Colemanite or 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. Wikipedia
Density: 2.42
Cleavage: perfect,, distinct
Color: Colorless, white, yellowish, grey
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: Massive granular to coarsely crystalline, most commonly nodular
Crystal system: Monoclinic
Formula (repeating unit): Ca2B6O11·5H2O