Schmiederite

Schmiederite is a secondary mineral in the oxidized zone of selenium-bearing hydrothermal base metal deposits. Its chemical formula is Pb₂Cu₂(Se⁴⁺O₃)(Se⁶⁺O₄)(OH)₄.^[3][4]

Schmiederite
General
Category	Selenate minerals
Formula	Pb2Cu2(Se4+ O 3)(Se6+ O 4)(OH)4
IMA symbol	Scm[1]
Strunz classification	7.BC.65
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/m
Unit cell	a = 9.92 Å, b = 5.71 Å c = 9.36 Å; β = 101.86°; Z = 2
Identification
Color	Pale to deep Prussian blue
Crystal habit	Fibrous in radial clusters; may be in crusts; powdery
Luster	Subadamantine to satiny
Streak	Light blue
Diaphaneity	Transparent
Specific gravity	5.62
Optical properties	Biaxial (+)
Refractive index	nα = 1.85–1.9 nβ = 1.9–1.95 nγ = 1.95–2.1
References	[2][3][4]

It was first described in 1962 for an occurrence in the Cóndor mine, Los Llantenes district, Sierra de Cacheuta, La Rioja Province, Argentina (type locality). It was named for Oscar Schmieder (1891–1980), German geographer.^[3]