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Hornßone. 3°3 32d Species. Hornftone. Hornilein of the Germans, Petrofiiex, Chert. Its colour commonly dark blue, yellowifb, or pearl grey, fometimes yellowifh white, flefh, or brownifh red, or monntain blue, or blackiflv brown, or greenifh brown, or dark green, or olive green, often variegated. Amorphous for the moft part, but lately found cryftallized by Mr. Beyer on Schneeberg, either in hexahrcdral prifms, fome with, fome withour, a pyramid, or barely rounded at both ends, or in double triangulär pyramids, or cubes or hexahae.- dral plates, the furface of thcfe cryftals moftly rough and uneven, fome hollow, fome folid, fometimes as thin as paper *. Its luftre, o. Tranfparcncy, 1.2. The cryf tallized, fometimes o. Its fra&ure generally fplintery, more rarely conchoidal, fometimes from the fine fplintery, paffing into the even, but of a coarfer grain than flint. Fragments, 2.3. Hardnefs, from 7 to 9. Sp. gr. from 2,532 to 2 > 6 53* Though Mr. Bergman counts this ftone among thofe rhat are fufible per fe, even by a blowpipe, yet, in the many trials I have made in a much fuperior heat, I found but one which gave any fign of fufion ; but moft frequently decrepitate and whiten. * 1 Crell. Beytr. p. 191. 3 Helvet. Miga. p. 251. lft,