Colemanite

CaB3O4(OH)3·H2O

This specimen features well-formed, blocky to prismatic crystals of colemanite, exhibiting a translucent to opaque white color and a vitreous luster.

Colemanite Physical Properties

Mohs Hardness

4.5

Crystal System

monoclinic

Luster

vitreous

Streak Color

white

Cleavage

perfect on {010}, good on {001}

Fracture

uneven to conchoidal

Specific Gravity

2.42

Colors

colorless, white, yellowish, grayish

Transparency

transparent to translucent

Type Locality

California, USA

Mineral Group

Borates

Uses

ore of boron, collector's specimen

Associated Minerals

ulexite, borax, gypsum, celestine

Rarity

uncommon

Geological Context

Colemanite forms in evaporite deposits, typically in arid lacustrine (lake) environments where boron-rich waters evaporate, leading to the precipitation of borate minerals.

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