Crookesite is a selenide mineral composed of copper and selenium with variable thallium and silver.

Characteristics

Its chemical formula is reported either as Cu
7
(Tl, Ag)Se
4
or (Cu, Tl, Ag)
2
Se
.[4] It is formed by precipitation from hydrothermal fluids, and contains by mass: 16.3% Tl, 47.3% Cu, 2.9% Ag, and 33.6% Se.[2]

Crookesite is an opaque, bluish grey to pink toned brown metallic mineral crystallizing in the tetragonal system. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 6.9.

Name and discovery

It was discovered in 1866 in Skrikerum, Sweden and named for Sir William Crookes (1832–1919), the discoverer of the element thallium.[2]

See also

References


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