tsumcorite

{{Infobox mineral | name = Tsumcorite | category = Arsenate minerals | boxwidth = | boxbgcolor = | image = Tsumcorite-160209.jpg | caption = Tsumcorite from the Tsumeb Mine, Namibia | formula = PbZnFe2+(AsO4)2.H2O | IMAsymbol = Tmc | molweight = 624.29 g/mol | strunz = 8.CG.15 | dana = 40.02.09.01 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/m (no. 12) | unit cell = a = 9.124 Å, b = 6.329 Å c = 7.577 Å; β = 115.3°; Z = 2 | color = Yellow-brown, red-brown, orange | habit = Radiating, fibrous crusts | twinning = Common, on an unknown law | cleavage = Good on {001} | fracture = | tenacity = | mohs = | luster = Vitreous | refractive = nα = 1.87–1.91 nβ = 1.89–1.93 nγ = 1.92–1.96 | opticalprop = Biaxial | birefringence = | pleochroism = Weak, yellow to yellow-green | 2V = 67–83.5° | streak = Yellow | gravity = 5.2 | melt = | fusibility = | diagnostic = | solubility = Dissolves in HCl | diaphaneity = Translucent | other = | references = }} Tsumcorite is a rare hydrated lead arsenate mineral that was discovered in 1971, and reported by Geier, Kautz and Muller. It was named after the TSUMeb CORporation mine at Tsumeb, in Namibia, in recognition of the Corporation's support for mineralogical investigations of the orebody at its Mineral Research Laboratory.

== Unit cell == Tsumcorite belongs to the monoclinic crystal class 2/m, which means that it has a twofold axis of symmetry along the b axis and a mirror plane perpendicular to this, in the plane containing the a and c axes. The a and c axes are inclined to each other at angle β = 115.3°. The unit cell parameters are a = 9.124 Å to 9.131 Å, b = 6.326 Å to 6.329 Å and c = 7.577 Å to 7.583 Å. There are two formula units per unit cell (Z = 2), and the space group is C2/m, meaning that the cell is a C-face centred lattice, with lattice points in the center of the C face as well as at the corners of the cell. The structure is related to the brackebushite group structure.