426 APPENDIX. 7• Crichtonite. « Craitonite, Sournon. Id. Bournon, Cat. Min. p. 430. External Characters. Its colour is velvet-black. It occurs crystallised in the following figures: 1. Very acute rhomboid, with angles of 18° and 162*; or it may be described as an acute double three sided pyramid, in which the lateral planes of the one are set on the lateral edges of the other. 2. In which the summits of the pyramids are more or less deeply truncated. 3. The summits of the pyramids acuminated with ^ three planes, which are set on the lateral planes, and the summits of the acumination truncated. 4. In which the angles of the summits of the pyra mids, are bevelled. The crystals are very small. Externally and internally it is splendent, and the lustre is vitreous, inclining to metallic. The fracture in one direction is foliated, in another conchoidal. It is opaque. It is harder than octahedrite ; it scratches fluor-spar^ but it does not affect glass. It does not affect the magnet. Chemical Characters. It is infusible without addition before the blowpipe. Gcognost i*
