Chondrodite

Chondrodite
General
Category	Nesosilicates
Formula (repeating unit)	Mg 5(SiO 4) 2F 2
IMA symbol	Chn[1]
Strunz classification	9.AF.45 (10th edition) 8/B.04-20 (8th edition)
Dana classification	52.3.2b.2
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/a
Identification
Formula mass	351.6 g/mol
Color	Yellow, orange, red or brown, rarely colorless
Crystal habit	Typically anhedral masses or grains, or as plates flattened on {010}, {001} or {100}.[2]
Twinning	Simple or multiple twinning common on {001}, also reported on {105} and {305}.[2]
Cleavage	Poor to good on (001)
Fracture	Conchoidal to uneven
Tenacity	Brittle
Mohs scale hardness	6 to 6.5
Luster	Vitreous to greasy
Streak	Grey or yellow
Diaphaneity	Translucent
Specific gravity	3.1 to 3.26
Optical properties	Biaxial(+)
Refractive index	nα = 1.592 – 1.643, nβ = 1.602 – 1.655, nγ = 1.619 – 1.675,
Birefringence	0.027 – 0.032
Pleochroism	X golden yellow to orange, Y and Z light yellow to almost colorless[3]
Solubility	Soluble in HCl and H2SO4
Other characteristics	Some specimens fluoresce orange yellow under shortwave and orange under longwave UV. Not radioactive.
References	[4][5][6][7][8]

Chondrodite is a nesosilicate mineral with formula (Mg,Fe)
₅(SiO
₄)
₂(F,OH,O)
₂. Although it is a fairly rare mineral, it is the most frequently encountered member of the humite group of minerals. It is formed in hydrothermal deposits from locally metamorphosed dolomite. It is also found associated with skarn and serpentinite. It was discovered in 1817 at Pargas in Finland, and named from the Greek for "granule", which is a common habit for this mineral.^[9]