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2 5 2 Siliceous Genus. fluxes, and yields only to bora^ and microcofmic lalt, with which it yields a clear glafs. 3d Family. Oriental Sapphire. Its colour, Berlin blue, but often decreafes f# much in intcnfity as to become almoft white, and then called lux fapphire. Its internal luftre, 3 or 4. Tranfparency, 3, 4, 2. Caufes fingle refradtion. * It is found cryftallized in the fame form as the preceding families, and often in rounded maffes the angles being worn ofFby fridlion. ’ Its frafture foliated. Its hardnefs, 17. Its fp. gr. 3991. It is infufible at 168 0 , and generally preferves its colour. It is affeded by the ufual fluxes, as the preceding gems. By the heat of pureair it forms an enamel. The fapphires, found amidft the fermginous fand of Expailly, near Puys in Velay, feem of this fpecies. Their colour, hardnefs, and tranf parency being fimilar, and their fp. gr. 4,076. They are very fmall, their form fomewhat 'irre gulär from the fridion they muft have encoun- tered. According to Mr. Bergman, this ftone contains 0,38 argil], 0,35 filex, 0,5 aerated calx, and 0,02 of tron. ßy Mr. Achard, 0,5833 argill, °>3333 0,0666 calx, 0,0333 of iron. To