( 522 CALC GENUS. fplintery frafture, fhow a tendency to flaty*, and the black variety has a conchoidal fracture. Fragments indeterminately angular, not particu larly fharp edged, and flaty. Sometimes prefents very fmall grained diftinft con cretions. Tranflucent on the edges or opaque, Pafles from femi-hard to foft. Not particularly brittle. Eafily frangible. When rubbed, emits an urinous fmelL Not particularly heavy. Chenfical Properties. When expofed to heat it lofes its colour and finell# and is converted into quick lime. It effervefces power- 1 fully with acids. Brochant. , Constituent Parts. jBefides lime and carbonic acid, which are its prin cipal conflituent parts, according to Vauquelin, k Contains-hydr fulphure, which is the caufe of the Imell it emits when rubbed, * The yellowifh brown variety is tv,oft commonly flaty. Qeognostic