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THE CHEMICAL ANALYSIS OP PRECIOUS STONES. 411
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GARNET.
Combination of a silicate of the protoxide of iron with silicate of alumina.
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The
native garnet (Almandine) is not electric by friction, but when
polished and facetted I have found by experiment that it becomes highly
so.
Native form : a rhombic dodecahedron, imbedded in mica-slate, and loose in the earth.
LAPIS-LAZULI.
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OPAL.
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PERIDOT: CHRYSOLITE.
Combination of magnesia, silica, and peroxide of iron.
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