5 12 CALC GENUS. 3. Oblique angular fix-fided pyramid, in which the alternate edges are obtufer than the •others* * The lens occurs fingle or in rows. Surface of the cryftals ufually drufy; the rhombs, ' however, are frriboth. Externally its luftre is fhining ; internally it alter nates from fhining to fplendent, but more frequently gliftening, and is always pearly. Fradture very frequently ftraight, but mod gene- rally fpherically curved foliated, and has a threefold obliquely interfering cleavage like calc fpar. $ Fragments rhomboidal. Occurs in granular diftindl concretions of all dc* grees of magnitude, but feldom fine grained ; alfo in ltraight lamellar concretions, which are very much grown together. More or lefs tranflucent, paffing into tranflucent on the edges ; the cryftals femitranfparent*. Semi-hard. Not particularly brittle. A little difficultly frangible. Not particularly heavy, approaching to heavy. It is heavier than calc fpar, but lighter than heavy fpar. Specific gravity -1,837. * When the tranfparency is very confidcrable it pafle* ‘ nt ° calc fpar. .Chen^