Sarkinite

Sarkinite
General
Category	Arsenate minerals
Formula (repeating unit)	Mn2(AsO4)(OH)[1]
IMA symbol	Srk[2]
Strunz classification	8.BB.15[1]
Dana classification	41.6.3.3[1]
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P2m[1]
Unit cell	a = 12.7795(13) Å b = 13.6127(14) Å c = 10.2188(11) Å β = 108.834(2)°; Z = 16[1]
Identification
Color	Red to yellow[1]
Crystal habit	Tabular[3] or granular[1]
Cleavage	Distinct on {100}[1]
Fracture	Irregular/Uneven, Conchoidal[1]
Mohs scale hardness	4–5[1]
Luster	Greasy[1]
Streak	Red to yellow[1]
Diaphaneity	Semitransparent[4]
Density	4.08 to 4.18 g/cm3 (measured)[1]
Optical properties	Biaxial (−)[1]
Refractive index	nα=1.793, nβ=1.807, nγ=1.809[1]
Birefringence	δ = 0.016[1]
Pleochroism	Weak[1]
2V angle	83° (measured)[1]
Dispersion	r > v or r < v[1]
Absorption spectra	X > Z > Y[1]
Solubility	Readily soluble in dilute acids[1]

Sarkinite, synonymous with chondrarsenite and polyarsenite, is a mineral with formula Mn₂(AsO₄)(OH). The mineral is named for the Greek word σάρκιυος, meaning made of flesh, for its red color and greasy luster. The mineral was first noted in Sweden in 1865 as chondrarsenite, though not identified as sarkinite until 1885.