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Ch. 20: Digests

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136             PRECIOUS STONES
The straw-yellow to greenish-yellow variety only is known commercially as chrysolite. In olive-green it is called peridot. The yellowish green variety, which is the mineralo­gist's olivine, is also known commercially as peridot. It is found in Egypt, Brazil, Mexico, Germany, Ceylon, South Africa, the United States, and in meteorites.
Crystallization trimetric; form, rhombic prism; usually found as water-worn pebbles.
Hardness, 6.5 to 7; specific gravity, 3.3 to 3.5; heavy according to the proportion of iron and consequent dark color.
Lustre vitreous to greasy; transparent to translucent; electric by friction.
Cleavage perfect, parallel to the smaller lateral plane; fracture conchoidal. It looks like glass except in the direc­tion of the cleavage.
Doubly refractive (index, 1.70 and 1.66) ; dichroic; twin colors of olive, brown-yellow and sea-green.
Composition varies: silica, 40; magnesia, 50; ferrous oxide, 9; nickel oxide, etc., I.
Excepting those containing much iron, it darkens but does not fuse under the blow-pipe, but fuses with borax to green glass and is attacked by sulphuric acid.
Color, yellow and various shades of olive-green.
Cut step and brilliant; does not hold sharp, fine edges to the facets.
Symbolizes gladsome heart; September, on the Jewish list of month stones.
Ch. 20: Digests Page of 237 Ch. 20: Digests
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