526 TALC FAMILY. The fragments are blunt-edged. It is opaque; very rarely feebly translucent on the edges. It is very soft. It is sectile. It is slightly elastic-flexible. It is difficultly frangible. It emits a grating sound when we handle it. It feels meagre. It is so light as to swim on water. Specific gravity, 0.679, 0.991, Brisson. 0.991, llamj. Chemical Characters. It melts with great difficulty before the blowpipe into a milk-white nearly translucent glass. Constituent Parts. Silica, 56.2 Magnesia, 26.1 xYlumina, 2.0 Lime, - - 12.7 Oxide of Iron, 3.0 100 Bergmann, Opusc. t. iv. Geognoslic Situation. It occurs in cotemporaneous veins in serpentine ; also in metalliferous veins in primitive and transition rocks > and occasionally in mineral beds. Geographic Situation. It occurs in veins in the serpentine of Portsoy; and i' 1 plates in the lead-veins at Lead Hills and Wanlockhead in Lanarkshire. At Sala in Sweden, it is in a metalli ferous