Safflorite

Safflorite
Safflorite and calcite from Morocco
General
Category	Arsenide mineral
Formula (repeating unit)	(Co,Fe)As2
Strunz classification	2.EB.15a
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pnnm
Unit cell	a = 5.173 Å, b = 5.954 Å c = 2.999 Å; Z = 2
Identification
Color	Tin white, tarnishes to gray
Crystal habit	Prismatic crystals, massive to fibrous
Twinning	Forms cruciform penetration twins
Cleavage	Distinct on {100}
Fracture	Uneven to conchoidal
Tenacity	Brittle
Mohs scale hardness	4.5-5.5
Luster	Metallic
Streak	Grayish black
Diaphaneity	Opaque
Specific gravity	6.9-7.3
References	[1][2][3]

Safflorite is a rare cobalt iron arsenide mineral with formula: (Co,Fe)As₂. Pure safflorite would be just CoAs₂, 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