Bornhardtite

bornhardtite

clausthalite

ferroselite

trogtalite

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Formula: Co2+Co3+2Se4
Selenide, bornhardtite subgroup, seleniospinel group, spinel supergroup, cobalt-bearing mineral
Crystal System: Isometric
Specific gravity: 6.166 calculated
Hardness: 4
Colour: Rose-red
Environments

Hydrothermal environments

Bornhardtite is of hydrothermal origin, and occurs associated with trogtalite, ferroselite and clausthalite (HOM).

Localities

At the type locality, the Trogtal Quarries, Harz, Goslar District, Lower Saxony, Germany, bornhardtite occurs as fine violet to red-brown intergrowths in clausthalite. Associated minerals include clausthalite, ferroselite, hematite, selenium and trogtalite (Mindat).

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