Crookesite
A variety of Minerals
What is Crookesite?
Crookesite is a selenide mineral composed of copper and selenium with variable thallium and silver.
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Key Characteristics
Characteristics of Crookesite
Its chemical formula is reported either as Cu7(Tl, Ag)Se4 or (Cu, Tl, Ag)2Se. 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. 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.
Quick Facts
Physical Properties
- Color
- Lead Grey
- Hardness (Mohs)
- 2.5 - 3
- Density
- 7.443 g/cm³
Chemical Properties
- Chemical Formula
- Cu7(Tl, Ag)Se4 Formely considered (Cu,Tl,Ag)2Se.
- Elements
- Ag, Cu, Se, Tl
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