Golden brown colemanite crystal cluster from Turkey showing a mirror reflection.
Macro photograph of transparent golden brown colemanite crystal faces from Turkey.
Interlocking amber brown colemanite crystals from Turkey against a black background.

Colemanite

Colemanite – CaB3O4(OH)3·H2O
Elements: Calcium, Boron, Oxygen, Hydrogen
Class: Borates
Crystal System: Monoclinic
Hardness: 4.5
Apatite
Talc (1)Diamond (10)
Softer than glass. A steel knife scratches it.
Origin: Kestelek Mine, Mustafakemalpasa District, Bursa Province – Turkey
Did you know?

Colemanite is a key source of the boron in heat-proof glass like Pyrex. Yet hold raw colemanite to a flame and the water locked inside flashes to steam so fast the mineral bursts and puffs up like popcorn.

More minerals containing Boron

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Dark brown dravite tourmaline crystal with sharp terminations from the USA.
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