473 CALC GFNUS. ^ It occurs moft commonly maffive, alfo in rolled pieces, in a variety of extraneous external fhapes, and in large tables (as that of Pappenheim). Internally it is dull. Fracture ■ fmall and-fine fplintery, which paflfes fcmctimes into large and flat corichoidal, fometimes into uneven, which approaches to earthy. One va riety has a tendency to the flaty fra&ure. Fragments indeterminately angular, more or lefs fitarp edged. Tran {lucent on the edges. Semi-hard. Brittle. Pretty eafily frangible. Not particularly heavy. Specific gravity—From 2,6co to 2.70c. I ' / Constituent Parts* It is principally compofed of lime and carbonic acid, and a fmall portion of iron, alumina, and inflammable matter. Geognostic Situation. This foffll conftitutes feveral very diftinft and highly chara&eriftic formations, concerning which a full detail will be given in the Geognofie, at pre; fcnt