Difference between revisions of "Almandine"
From The Gemology Project
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==Inclusions== | ==Inclusions== | ||
[[Image:Sk_garnet_silk.jpg|thumb|left|240px|Silk, crystals, and a crystal looking like a skull, inside of a pyrope-almandine garnet.<br />~85X Magnification<br /> ©Jamey Swisher]] | [[Image:Sk_garnet_silk.jpg|thumb|left|240px|Silk, crystals, and a crystal looking like a skull, inside of a pyrope-almandine garnet.<br />~85X Magnification<br /> ©Jamey Swisher]] | ||
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==Localities== | ==Localities== |
Revision as of 21:06, 6 September 2010
Almandine Garnet | |
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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 |
Contents
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.
Inclusions
Localities
India, USA, Brazil
Occurrence
Metamorphic rocks