Berzelianite

selenide

umangite

Formula:Cu2-xSe (x is approximately 0.12)
Selenide, dimorph of bellidoite, berzelianite - umangite group, forms a complete solid-solution series with high digenite (cubic, high-temperature digenite (Mindat).
Specific gravity: 6.71
Hardness: 2
Streak: Shining
Colour: Silver-white, shiny lead-grey; easily tarnishes iridescent blue-grey
Solubility:
Environments

Hydrothermal environments

Berzelianite occurs with other selenides in hydrothermal veinlets in dolostone (Webmin). Associated minerals include eucairite, clausthalite, tiemannite, umangite, klockmannite, aguilarite, crookesite, athabascaite, stromeyerite, polybasite, pearceite, gold, uraninite, pyrite, marcasite and calcite (HOM, Mindat).

At Lake Athabaska, North West Territories, Canada, berzelianite occurs as blebs and veinlets in calcite gangue associated with umangite and chalcocite (AM 35.337-364).

At Clausthal, Lower Saxony, Germany, berzelianite occurs with other selenides in hydrothermal veinlets in dolostone (HOM).

At Lerbach, Lower Saxony, Germany, berzelianite occurs in iron ores (HOM).

At the type locality, the Skrikerum Mine, Valdemarsvik, Östergötland County, Sweden, berzelianite occurs with other selenides in calcite veins in serpentine (HOM, AM 35.337-364).

At Redjang-Lebong, Sumatra, berzelianite occurs in a gold - quartz - orthoclase deposit (HOM).

At Urora, Nevada, USA, berzelianite is disseminated in a highly weathered siliceous gangue associated with native gold and lead (AM 35.337-364).

Common impurities: Ag,Tl

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