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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
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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