Difference between revisions of "Almandine"

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m (Specific gravity)
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===Specific gravity===
 
===Specific gravity===
  
Sinks in all common heavy liquids
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Almandine sinks in all common heavy liquids.
  
 
===Optical effects===
 
===Optical effects===

Revision as of 10:16, 13 December 2006

Almandine Garnet
Chemical composition Fe3Al2(SiO4)3

Iron aluminum silicate

Crystal system Cubic
Habit Dodecahedra
Cleavage None
Hardness 7.5
Optic nature Isotropic
Refractive index 1.78-1.81
Birefringence None
Specific gravity 3.95 - 4.20
Lustre Vitreous

Diagnostics

Color

Brownish red, red to violet/purple

Spectroscope

Almandine has a typical iron spectrum

Inclusions

  • Short rutile needles in 3 directions
  • Crystals surrounded by stress cracks
  • Irregular and rounded crystals

Polariscope

Almandine is isotropic but may have a small DR.

Specific gravity

Almandine sinks in all common heavy liquids.

Optical effects

Almandine may show asterism and chatoyancy

Varieties

Rhodolite

Rhodolite is the purple (pinkish/violet) variety of pyrope-almandine.

Localities

India, USA, Brazil

Occurance

Metamorphic rocks