Stilpnomelane

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Stilpnomelane
Specific gravity
2.77 – 2.96
Optical propertiesBiaxial (−)
Refractive indexnα = 1.543 – 1.634 nβ = 1.576 – 1.745 nγ = 1.576 – 1.745
Birefringenceδ = 0.033 – 0.111
PleochroismX: bright golden yellow to pale yellow Y and Z: deep reddish brown, to deep green to nearly black
2V angle
0–40 measured
DispersionNone
References[2][3][4]

Stilpnomelane is a

phyllosilicate mineral. It has the chemical formula K(Fe2+,Mg,Fe3+)8(Si,Al)12(O,OH)27·n(H2O).[4]

Stilpnomelane occurs associated with

metamorphic mineral associated with the blueschist and greenschist facies.[2]

It was first described in 1827 for an occurrence in Moravia in the Czech Republic. The name is derived from the Greek stilpnos for shining, and melanos for black.[3]

References

  1. S2CID 235729616
    .
  2. ^ a b Handbook of Mineralogy
  3. ^ a b Stilpnomelane on Mindat
  4. ^ a b Stilpnomelane on Webmineral



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