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Ch. 8: Other Stones Used in Jewelry

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204                   Lapis Lazuli.
and is found in masses; it has a hardness of 5.3, a specific gravity of 2.38 to 2.45, a subvitreous lustre of a rich blue colour, and is opaque.
The composition of the Persian variety is, according to Klaproth :—
It fuses to a white glass, and, if calcined and reduced to powder, loses its colour, and gelatinizes in muriatic acid ; with borax it effervesces, and forms a colourless glass.
Lapis lazuli is usually found in granite or calcareous limestone, with iron pyrites, often disseminated through the mass, which, when polished, gives it the gold-spotted appearance it often exhibits : the finest quality comes from Persia and Beloochistan ; it is also found in China, Bucharia, and in Siberia. Latterly large quan­tities of very inferior quality and colour have been brought from Chili. The deep-coloured pieces are the most esteemed, being extensively used for studs, brooches, and other articles of jewellery, as well as for vases, ornamental furniture, mosaic work, etc. ; when ground to powder, they form the valuable pigment called ultramarine. Latterly, however, chemists have
Ch. 8: Other Stones Used in Jewelry Page of 295 Ch. 8: Other Stones Used in Jewelry
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