Selenide, thallium-bearing mineral
Specific gravity: 6.90
Hardness: 2½ to 3
Common impurities: Fe
Crookesite is of hydrothermal origin; associated minerals include umangite,
linnaeite, calcite and
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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