Langite

Langite is a rare hydrated copper sulfate mineral, with hydroxyl, found almost exclusively in druses of small crystals. It is formed from the oxidation of copper sulfides, and was first described in specimens from Cornwall, United Kingdom. It is dimorphous with wroewolfeite. Langite was discovered in 1864 and named after the physicist and crystallographer Viktor von Lang (1838–1921), who was Professor of Physics at the University of Vienna, Austria.

Langite is a rare hydrated copper sulfate mineral, with hydroxyl, found almost exclusively in druses of small crystals. It is formed from the oxidation of copper sulfides, and was first described in specimens from Cornwall, United Kingdom. It is dimorphous with wroewolfeite. Langite was discovered in 1864 and named after the physicist and crystallographer Viktor von Lang (1838–1921), who was Professor of Physics at the University of Vienna, Austria. Langite belongs to the monoclinic crystal class m, meaning that it has just one mirror plane, and no axes of rotational symmetry. The crystal is built up of identical unit cells stacked together, with no space in between. The unit cell for the monoclinic system has a base which is a rhombus, with sides a and c inclined at angle β. The third side b is perpendicular to both a and c. For langite the angle β is very close to 90°, so the unit cell is almost brick-shaped (as for the orthorhombic system). Different sources give slightly different values for the unit cell parameters, but they all fall within the ranges a = 7.118 Å to 7.137 Å, b = 6.031 Å to 6.034 Å, c = 11.209 Å to 11.217 Å, β = 90.00 to 90.02°, Z (the number of formula units per unit cell) = 2. N x = 1.641, N y = 1.690, N z = 1.712 N x = 1.708, N y = 1.760, N z = 1.798 N x = 1.641 to 1.654, N y = 1.690 to 1.713, N z = 1.705 to 1.722 N x = 1.641, N y = 1.690, N z = 1.705 to 1.712 The mineral is pleochroic, with X light yellowish green, Y blue-green and Z sky blue. Jmol: https://rruff.geo.arizona.edu/AMS/viewJmol.php?id=09777

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