Purpurite

Purpurite is a mineral, manganese phosphate, MnPO₄ with varying amounts of iron depending upon its source. It occurs in color ranges from brownish black via purple and violet to dark red.[2]

Purpurite
Purpurite from Namibia
General
Category	Phosphate minerals
Formula (repeating unit)	Mn3+PO4
Strunz classification	8.AB.10
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pnmb
Identification
Formula mass	149.91 g/mol
Color	Brownish black, violet, dark pink, dark red, reddish purple
Crystal habit	Massive to granular
Cleavage	[100] [001] perfect
Fracture	Brittle - uneven
Mohs scale hardness	4-5
Luster	Earthy
Streak	red
Specific gravity	3.2 - 3.4
Optical properties	Biaxial (+) 2V 38°
Refractive index	nα = 1.850(2) nβ = 1.860(2) nγ = 1.920(2)
Birefringence	δ = 0.070
Other characteristics	non-radioactive, non-magnetic, non-fluorescent.
References	[1][2][3]

Purpurite forms a series with the iron-bearing endmember heterosite, FePO₄.[3]