Crookesite

minerals

umangite

berzelianite

eucairite

Formula: Cu7TlSe4
Selenide
Specific gravity: 6.90
Hardness: 2½ to 3
Colour: Lead-grey
Common impurities: Fe
Environments

Hydrothermal environments

Crookesite is of hydrothermal origin; associated minerals include umangite, berzelianite, eucairite, klockmannite, clausthalite, sabatierite, selenium-bearing linnaeite, calcite and quartz (HOM).

Localities

At the Bukov mine, Rožná deposit, Rožná, Žďár nad Sázavou District, Vysočina Region, Czech Republic, crookesite occurs in a vein-replacement deposit, associated with bukovite and sabatierite (AM 73.933).

At the type locality, the Skrikerum mine, Valdemarsvik, Östergötland County, Sweden, crookesite occurs in hydrothermal deposits as finely disseminated specks and small veinlets, in translucent calcite with minor quartz (AM 35.337-364).

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