Chondrodite

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.

Chondrodite
General
CategoryNesosilicates
Formula
(repeating unit)
Mg
5
(SiO
4
)
2
F
2
IMA symbolChn
Strunz classification9.AF.45 (10th edition)
8/B.04-20 (8th edition)
Dana classification52.3.2b.2
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/a
Identification
Formula mass351.6 g/mol
ColorYellow, orange, red or brown, rarely colorless
Crystal habitTypically anhedral masses or grains, or as plates flattened on {010}, {001} or {100}.
TwinningSimple or multiple twinning common on {001}, also reported on {105} and {305}.
CleavagePoor to good on (001)
FractureConchoidal to uneven
TenacityBrittle
Mohs scale hardness6 to 6.5
LusterVitreous to greasy
StreakGrey or yellow
DiaphaneityTranslucent
Specific gravity3.1 to 3.26
Optical propertiesBiaxial(+)
Refractive indexnα = 1.592 – 1.643, nβ = 1.602 – 1.655, nγ = 1.619 – 1.675,
Birefringence0.027 – 0.032
PleochroismX golden yellow to orange, Y and Z light yellow to almost colorless
SolubilitySoluble in HCl and H2SO4
Other characteristicsSome specimens fluoresce orange yellow under shortwave and orange under longwave UV. Not radioactive.
References
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