Almandine

General Information about Almandine

• Belongs to the garnet group
• Name derived from alabandicus, used by Pliny the Elder
• Iron alumina garnet with deep red to purple color
• Often cut with a convex face, known as carbuncle
• Shows three characteristic absorption bands when viewed through the spectroscope

Crystal Structure and Composition

• Almandine is one end-member of a mineral solid solution series
• Other end-member is the garnet pyrope
• Crystal formula: Fe(SiO)
• Magnesium can substitute for the iron with more pyrope-rich composition
• Crystallizes in the cubic space group a3d, with a unit-cell parameter of approximately 11.512Å at 100K

Occurrence

• Abundant in gem gravels of Sri Lanka, sometimes called Ceylon ruby
• Violet-tinted almandine is known as Syriam garnet
• Large deposits found in the Northern Territory of Australia, initially mistaken for rubies
• Found in schistose rocks of the Zillertal in Tyrol
• Almandine with partial magnesia substitution found at Luisenfeld in German East Africa

Uses and Properties

• Almandine is used as an abrasive agent when crushed
• Widely distributed in the United States
• Fine crystals embedded in mica-schist found near Wrangell in Alaska
• Specific gravity of 4.05+0.25−0.12
• Luster ranges from greasy to vitreous

Cultural Significance and References

• Connecticut has designated almandine garnet as its state gemstone
• Almandine is listed in the Handbook of Mineralogy
• References include publications such as Mineralogical Magazine and GIA Gem Reference Guide
• Almandine is featured in Wikimedia Commons
• Other related topics include a list of minerals and the state symbols of Connecticut

Almandine Data Sources