Cervantite

Cervantite
240px Microscopic cervantite crystals from Slovakia (3 mm field of view)
General
Category	Oxide mineral
Formula (repeating unit)	Sb3+Sb5+O4
Strunz classification	04.DE.30
Crystal symmetry	Orthorhombic pyramidal H-M symbol: (mm2) Space group: Pbn21
Unit cell	a = 5.43 Å, b = 4.81 Å, c = 11.76 Å; Z = 4
Identification
Color	Yellow to nearly white
Crystal habit	Microscopic acicular crystals; massive
Crystal system	Orthorhombic
Cleavage	Excellent on {001}, distinct on {100}
Fracture	Conchoidal
Mohs scale hardness	4–5
Luster	Greasy, pearly, earthy
Streak	Pale yellow to white
Diaphaneity	Semitransparent
Specific gravity	6.5
Optical properties	Biaxial
Refractive index	nα = 2.000 nγ = 2.100
Birefringence	δ = 0.100
Dispersion	relatively weak
References

Cervantite is an antimony oxide mineral with formula Sb³⁺Sb⁵⁺O₄ (antimony tetroxide).

It was first described in 1850 for an occurrence in Cervantes, Sierra de Ancares, Lugo, Galicia, Spain, and named for the locality. The mineral was questioned and disapproved, but re-approved and verified in 1962 based on material from the Zajaca-Stolice district, Brasina, Serbia. It occurs as a secondary alteration product of antimony bearing minerals, mainly stibnite.

File:Valentinite-Cervantite-Stibnite-213068.jpg

Cervantite and valentinite replacing stibnite from the Xikuangshan Mine of Hunan Province, China (size: 16.1 x 5.0 x 3.0 cm)