Sarkinite

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.

Sarkinite
General
Category	Arsenate minerals
Formula	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]

Description

Sarkinite is red to yellow in color. It occurs as thick tabular crystals, short prismatic crystals, or has a granular habit. Sarkinite sometimes aggregates into a roughly spherical shape. Sarkinite is a member of the Wagnerite Group.^[1]

The mineral occurs in manganese-rich lenses in quartzitic chlorite schists, metamorphosed zinc ore bodies, and rarely in metamorphosed Fe–Mn ore bodies.^[4]

Structure

Sarkinite is isostructural with triploidite and wolfeite^[1] and is a dimorph of eveite.^[5] The crystal structure consists of MnO₄(OH)₂ octahedra, MnO₄(OH) trigonal bipyramids, and AsO₄ tetrahedra.^[6]

History

In 1885, two similar minerals were discovered in Sweden. Polyarsenite was found in Grythyttan and named by Igelström for its high arsenic content. Sarkinite was discovered in Pajsberg, Persberg, and named by A. Sjögren after the Greek word σάρκιυος, meaning made of flesh, in reference to the blood-red color and greasy luster. It was considered likely that the two minerals were identical.^[7] A study in 1980 showed that polyarsenite and chondrarsenite, discovered in 1865, were in fact both sarkinite.^[8]

Distribution

As of 2012^[update], sarkinite has been found in Austria, France, Italy, Japan, Kazakhstan, Romania, Sweden, Switzerland, and the United States.^[1]

Association

Sarkinite has been found in association with:^[4]

Harstigen mine, Sweden

• Barite, bementite, brandtite, calcite, lead

Sjö mine, Sweden

• Jacobsite, katoptrite, magnetite, tephroite

Ködnitz Valley, Austria

• Pyroxmangite, rhodochrosite, rhodonite, spessartine, tephroite, tiragalloite

Falotta mine, Switzerland

• Brandtite, braunite, grischunite, manganoan berzeliite, rhodochrosite, tilasite

Sterling Hill, New Jersey, US

• Adamite, allactite, barite, brandtite, copper, euchroite, eveite, kraisslite, manganese oxides, parabrandtite, rhodochrosite, serpierite, willemite