Difference between revisions of "Almandine"
From The Gemology Project
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[[Image:Rhodolite_Garnet_7.jpg|left|framed|Faceted Rhodolite Garnet <br /> Photo courtesy of Rick Martin]]<br clear="left" /> | [[Image:Rhodolite_Garnet_7.jpg|left|framed|Faceted Rhodolite Garnet <br /> Photo courtesy of Rick Martin]]<br clear="left" /> | ||
Rhodolite is the purple (pinkish/violet) variety of pyrope-almandine. | Rhodolite is the purple (pinkish/violet) variety of pyrope-almandine. | ||
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| + | ==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]] | ||
==Localities== | ==Localities== | ||
Revision as of 21:03, 6 September 2010
| 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 |
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
Faceted Rhodolite Garnet
Photo courtesy of Rick Martin
Photo courtesy of Rick Martin
Rhodolite is the purple (pinkish/violet) variety of pyrope-almandine.
Inclusions
Localities
India, USA, Brazil
Occurrence
Metamorphic rocks
