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Ch. 2: Classification Gemstones

Ch. 2: Classification Gemstones Page of 451 Ch. 2: Classification Gemstones Text size:minus plus Restore normal size   Mail page  Print this page
Classifications of Stones          13
A. Gems of the First Rank
Hardness, between 8 and 10. Consisting of pure carbon, or pure alumina, or with alumina predominating. Fine specimens of very rare occurrence and of the highest value.
B. Gems of the Second Rank
Hardness, between 7 and 8 (except precious opal). Specific gravity usually over 3. Silica a prominent constituent. In specimens of large size and of fairly frequent occurrence. Value generally less than stones of Group A, but per­fect specimens are more highly prized than poorer specimens of Group A.
C. Gems of the Third Rank
These are intermediate in character, between the true gems and the semi-precious stones. Hardness between 6 and 7. Specific gravity usually greater than 2.5. With the exception
Ch. 2: Classification Gemstones Page of 451 Ch. 2: Classification Gemstones
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