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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
14 A Book of Precious Stones
of turquoise, silica is a prominent constituent of all these stones. Value usually not very great; only fine specimens of a few members of the group (cordierite, chrysolite, turquoise) have any considerable value. Specimens worth cutting of comparatively rare occurrence, others fairly frequent.
2. Semi-Precious Stones
These have some or all of the distinguishing characters of precious stones, but to a less marked degree.
D. Gems of the Fourth Bank
Hardness, 4-7. Specific gravity 2-3 (with the exception of amber). Colour and lustre are frequently prominent features. Not as a rule perfectly transparent: often translucent, or translucent at the edges only. Wide distribu­tion. Value, as a rule, small.
Ch. 2: Classification Gemstones Page of 451 Ch. 2: Classification Gemstones
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