September Mineral of the Month – Garnet

close-up of garnets

Garnet

Chemical Formula: Garnet is a series of several different minerals with unique chemical formulas. The Garnet mineral group is compromised of isomorphous minerals identical in crystal structure and in many cases difficult to determine one from another. The members of this group intermingle with one another, within limits.
The simple chemical formula of the group is:
X2+3Y3+2Si3O12
Color: Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black
Hardness: 6.5 - 8.5
Crystal System: Isometric
Refractive Index: 1.780 - 1.889
SG: 3.5 - 4.3
Transparency: Transparent to translucent
Double Refraction: None
Luster: Vitreous; some forms adamantine or submetallic
Cleavage: None. May exhibit parting.
Mineral Class: Garnet