Keyite | |
---|---|
General | |
Category | Arsenate minerals |
Chemical formula | Cu2+ 3Zn 4Cd 2(AsO 4)6 · 2H 2O |
Strunz classification | 08.CA.50 |
Crystal symmetry | 2/m |
Unit cell | a = 11.654(3) Å, b = 12.780(5) Å, c = 6.840(3) Å, β = 99.11° |
Identification | |
Molar mass | 1,520.19 g |
Color | azure/blue |
Crystal habit | prismatic, tabular |
Crystal system | monoclinic – prismatic |
Cleavage | good (001) cleavage |
Mohs scale hardness | 3.5 - 4 |
Streak | light blue |
Diaphaneity | translucent |
Density | 5.106g/cm3 |
Optical properties | biaxial |
Refractive index | nα = 1.800, nβ, and nγ = 1.870 |
Birefringence | 0.070 |
Pleochroism | x: pale blue, y: greenish blue, z: deep blue |
References | [3] |
Keyite is a mineral with the chemical formula Cu2+
3Zn
4Cd
2(AsO
4)6 · 2H
2O.[4] The name comes from Charles Locke Key (1935-present), an American mineral dealer who furnished its first specimens.[5] Keyite is monoclinic-prismatic, meaning its crystal form has three unequal axes, two of which have 90° angles between them and one with an angle less than 90°.[6] Keyite belongs to the biaxial optical class, meaning it has more than one axis of anisotropy (optic axis), in which light travels with zero birefringence, and three indices of refraction, nα = 1.800, nβ, and nγ = 1.870[7][8]. Being a very rare cadmium copper arsenate, keyite is only found in Tsumeb, Namibia in the Tsumeb mine, a world famous copper mine known for its abundance of rare and unusual minerals.[9]