Group A. Isolates gems with a specific gravity of 4.7963 and over 4.70; in this group is placed zircon, with a specific gravity of from 4.70 to 4.88.
Group B. Stones whose specific gravity lies between 3.70 and under 4.7963.
Garnets, many varieties.
Almandine 4.11 and occasionally to 4.25
Ruby 4.073 ” 4.080
Sapphire 4.049 ” 4.060
Corundum 3.90 ” 4.16
Cape Ruby 3.861
Demantoid 3.815
Staurolite 3.735
Malachite 3.710 and occasionally to 3.996
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