500 CALC GENUS. Internally its luftre is moft commonly glimmering, fometimes palling to gliftening, and is pearly. ^ Frafture ftraight, fcopiformly, and ftellularly diverging fibrous; and is from very delicately fibrous to coarfe fibrous, which is nearly radiated. Fragments fometimes indeterminately angular, fel- dom fplintery and wedge-lhaped. It occurs moft commonly in curved lamellar diftinft concretions, which are bent in the direction of the external furface; in the ftalaffitic and tubular varifi' ties it has cylindrical convex concretions. Some times, although rarely, we find it in large and coarfe grained diftinft concretions. More or lefs tranllucent, and fome varieties ap proach to femi-tranfparent. Semi-hard, approaching to foft. Brittle. Eafily frangible. Not particularly heavy. sGeognostic Situation. It is found ftala&itic and tubular, alfo reniform> botroidal, and in crufts, that hang from, or covet the roofs, walls, and floors of caves, which are ufualty in limeftone. The beautiful ccralloidal vaiiety, the fios fcrri of fome mineralogifts, is found in veins of fparry h'° n ftone. From its peculiar external fliape, and its oc currence in drufy cavities, I am inclined to believe ]t ough c