Hedenbergite

Hedenbergite
General
Category	Pyroxenes
Formula (repeating unit)	CaFeSi2O6
IMA symbol	Hd[1]
Strunz classification	9.DA.15
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/c
Identification
Formula mass	248.09 g/mol
Color	brownish green, black
Crystal habit	massive, prismatic crystals
Cleavage	Good on {110}
Fracture	Irregular
Tenacity	Brittle
Mohs scale hardness	5.5–6.5
Luster	Vitreous, dull
Streak	white, gray
Diaphaneity	Transparent-Opaque
Density	3.56 g/cm3
Optical properties	Biaxial (+)
Refractive index	nα = 1.699 – 1.739 nβ = 1.705 – 1.745 nγ = 1.728 – 1.757
Birefringence	δ = 0.029
Pleochroism	Weak
Dispersion	r > v strong
References	[2][3]

Hedenbergite, CaFeSi₂O₆, is the iron rich end member of the pyroxene group having a monoclinic crystal system. The mineral is extremely rarely found as a pure substance, and usually has to be synthesized in a lab. It was named in 1819 after M.A. Ludwig Hedenberg, who was the first to define hedenbergite as a mineral. Contact metamorphic rocks high in iron are the primary geologic setting for hedenbergite. This mineral is unique because it can be found in chondrites and skarns (calc–silicate metamorphic rocks). Since it is a member of the pyroxene family, there is a great deal of interest in its importance to general geologic processes.