Volltext Seite (XML)
'Foliated, 85 Its fradtu re foliated, often very fmall and fine, always ftraight, fometimes in the grofs flaty. Its fragments 2. It prefents granulär diftindt concretions, often fb fmall and fine, that the foliated texture is dif- ficultly difcerned. Its hardnefs from 7 to 8; its fpec. grav. from 2,71 to 2,8376; where the denfity is higher, it is impure. It fcarcely ever contains petrifadlions, or im- preffions of marine exuviae. Many of thefe effervefce very flowly with acids, as will be feen in the fequel. Parian marble is faid to be the pureft ftone of this family. Its colour is pure white. Its fpec. grav. according to Brifibn, 2,8376. Carrara marble is next in purity. I found it to contain about 0,45 of fixed air, and 0,03 of argill, with minute quartz cryftals. Its fpec. grav. ^,717. Mr. Cronfted, in the Memoirs of Stockholm for the year 1763, teils us he metin Iempthmd a black thin flaty limeftone, of a fparry texture, which, from its external appearance, would fcarcely be taken for limeftone, and yet afforded excellent lime. In fome places it was dark grey, and undulatingly flaty. . Mr. Woulfe prefented me with another of the flaty kind from Scotland ; its colour dark bluifh grey; its luftre 1; tranfparency 1 ; fradture, thick flaty. The lamina» about the thickneJs of an inch ; their furfaces ftrewed over with mica. Fradlure of the lamin$ granularly foliated, yet mixed with the iplintery. Fragments 3; hard* nefs from 8 to 9; fpec. grav. 2,718. Some limcflones are at the lame time both granulär and fine fplintery, as may be feen in the G 3 fpe.