214 FLINT GENUS. 2. In rectangular four-fided priftns, acuminated on both extremities by four planes, which are fet on the lateral planes : fometimes the prihns are fo thin that they may be viewed as longifh fix-fided tables, bevilled on their four fmaller terminal planes; fometimes two of the terminal planes became fo large as nearly to lorm an oblique four-fided table. The cryftalsare often manipularly aggregated, and frequently fo grown together that the acuininations only are vifible, and projeCt like pyramids. The cry- Hals are middle fized and fmall. The broader lateral planes are fmooth, and longitudinally Iheathed. External luftre fhining, approaching to fplendent and pearly. Internally gliltening and completely pearly. Fracture narrow and broad, ftraight and curved, and ftellularly and fcopiformly diverging—radiated. The broad radiated borders on the foliated, and the narrow on the fibrous fraCture. Fragments fometimes indeterminately angular, fometimes wedge-Ihaped. It occurs in large and coarfe, even fometimes ap proaching to the fmall grained, longilh diftinCt con cretions. It is tranflucent; the cryftals are fometimes fern 1 * tranfparent and duplicating tranfparent *. * Hanr. Semi-hard;
