Chemistry:Safflorite

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Safflorite
Safflorite and Calcite3 - Bouismas Mine, Bou Azzer, Tazenakht, Ouarzazate, Souss-Massa-Draa, Morocco.jpg
Safflorite and calcite from Morocco
General
CategoryArsenide mineral
Formula
(repeating unit)
(Co,Fe)As
2
Strunz classification2.EB.15a
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnnm
Unit cella = 5.173 Å, b = 5.954 Å
c = 2.999 Å; Z = 2
Identification
ColorTin white, tarnishes to gray
Crystal habitPrismatic crystals, massive to fibrous
TwinningForms cruciform penetration twins
CleavageDistinct on {100}
FractureUneven to conchoidal
TenacityBrittle
Mohs scale hardness4.5-5.5
|re|er}}Metallic
StreakGrayish black
DiaphaneityOpaque
Specific gravity6.9-7.3
References[1][2][3]

Safflorite is a rare cobalt iron arsenide mineral with the chemical formula (Co,Fe)As
2
. Pure safflorite is CoAs
2
, but iron is virtually always present. Safflorite is a member of the three-way substitution series of arsenides known as the loellingite or loellingite group. More than fifty percent iron makes the mineral loellingite whereas more than fifty percent nickel and the mineral is rammelsbergite. A parallel series of antimonide minerals exist.

Safflorite along with the other minerals crystallize in the orthorhombic system forming opaque gray to white massive to radiating forms, Clinosafflorite has a monoclinic symmetry. It has a mohs hardness of 4.5 and a specific gravity of 6.9 to 7.3. Twinning is common and star shaped twins are frequently found.

Polished sample of safflorite, loellingite and rammelsbergite on quartz from the St Andreasberg District, Harz Mountains

It was first described in 1835 from the Schneeberg District, Erzgebirge, Saxony, Germany . Safflorite occurs with other arsenide minerals as an accessory in silver mining districts. It alters to the arsenate erythrite in the secondary environment.

References