302 ZEOLITE FAMILY. Externally the crystals are shining, passing into splen dent. Internally it is glistening, and the lustre is vitreous, inclining to pearly. The principal fracture is very narrow, straight, and scopiform radiated, which sometimes passes into fihrous. The cross fracture is small and fine-grained uneven. The crystals have a double cleavage. It breaks into splintery and wedge-shaped fragments. ^ It occurs in large and coarse granular distinct concre tions, and each of these is composed of very thin and straight prismatic concretions, which at their free extre mities generally shoot into crystals. It is translucent: the crystals are semi-transparent and transparent; and it refracts double. It is semi-hard ; it scratches calcareous-spar. It is brittle; and Eather heavy, approaching to light. Specific gravity, 2.179, 2.198, 2.270, Iloffmann. Chemical Characters. It intumesccs before the blowpipe, and forms a jelly with acids. Physical Characters. It becomes electric by heating, and retains this pro- pert} some time after it has cooled. The free extremity of the crystal, with the acumination, shews positive, and the attached end negative electricity.—Hauy. Constituent
