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alum-stone. 4.07 fid by tiie decomposion of iron-pyrites: the sulphuric acid thus formed is supposed to unite with the lime and alu mina ; with the lime it forms sulphate of lime or selenite, and with the alumina an alum, with a superabundance of alumina. 2. Alum-Stone. Alaunstein, Werner. Cadcareus aluminaris albus, Wall. t. ii. p. 34.—Alumen mar- moiis, Breislac, Sagg. di Observ. sulla Tolfa, &c. Horn. 1791). Svo Alaunstein, JV'td. s. 39!).—Pictra d’Allume, Nap. p. 2G(i.—Alumenilite, La Melh. t. ii. p. 113—La pierrc alumincuse, Brock, t. i. p. 381—Alaunstein, Ileusa, b. ii. 2. s. 139- Id. Lud. b. i. s. 109- LI Suck. b. i. s. 52fi. Id. Bert. s. 279. LI. Molts, b. i. s. 445. Id. Leonhard, Tabel. s. 22. Id. Karat. Tabel. s. 3(). Id. Steffens, b. i. s. 14->. Id. Lcnz, b. ii. s. 567. Li. Oken, 1). i. s. Extcrnal Characters, Its colours are greyish-white, snow-white, reddish- white, seldom yellowish-white, and spotted brown, and peach-blossom-red. It occurs massive, sometimes porous, and the pores have a crystalline drusy appearance. Internally it is feebly glimmering, passing into dull. The fracture is small-grained uneven, sometimes passi ng into splintery, sometimes into earthy. ■1'he fragments are sharp-edged. It is semi-hard in a low degree. It is feebly translucent on the edges. It is brittle, and easily frangible. Specific gravity, 2.597, IT. 2.633, Karstcn. C c 4, Chemical
