Chemical composition -- The garnets comprise a family of complex silicates with widely varying chemical composition but similar structures. While everyone is familiar with dark brownish or purplish red garnets, many are unaware that garnets can occur in almost any color except blue (although there have been some recent reports of some color change garnets that are predominantly blue). Slight variations in chemical composition define the placement of a garnet within the family.
Optics -- R.I. varies with composition, but generally 1.74-1.94. Isometric.
Durability -- Hardness 6.5-7.5.
Crystal structure -- Isometric (cubic).
Specific Gravity -- 3.4-4.2
Varieties -- Many garnets are mixtures of the primary varieties and show variations in properties according to the specific composition.
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