Almandine

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

Oval, faceted Almandine garnet

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

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

Inclusions

Silk, crystals, and a crystal looking like a skull, inside of a pyrope-almandine garnet.
~85X Magnification
©Jamey Swisher

Localities

India, USA, Brazil

Occurrence

Metamorphic rocks