Garnet

Garnet
Garnet
General
Category	Nesosilicate
Formula ; (repeating unit)	The general formula X 3 Y 2 (SiO 4 ) 3
Identification
Color	virtually all colors, blue very rare
Crystal habit	Rhombic dodecahedron or cubic
Cleavage	Indistinct
Fracture	conchoidal to uneven
Mohs scale hardness	6.5?7.5
Luster	vitreous to resinous
Streak	White
Specific gravity	3.1?4.3
Polish luster	vitreous to subadamantine
Optical properties	Single refractive, often anomalous double refractive
Refractive index	1.72?1.94
Birefringence	None
Pleochroism	None
Ultraviolet fluorescence	variable
Other characteristics	variable magnetic attraction
Major varieties
Pyrope	Mg 3 Al 2 Si 3 O 12
Almandine	Fe 3 Al 2 Si 3 O 12
Spessartine	Mn 3 Al 2 Si 3 O 12
Andradite	Ca 3 Fe 2 Si 3 O 12
Grossular	Ca 3 Al 2 Si 3 O 12
Uvarovite	Ca 3 Cr 2 Si 3 O 12

A garnet / ? ? ?ːr n ? t / is one kind of silicate mineral. There are many different kinds of garnets, containing different metals. Crystals of garnet are often large and pretty. Their most common color is red or purple, but they can be found in almost all colors and are often used in jewelry. In the United States , garnet is the birthstone for people born in the month of January .