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26 HORNBLENDE FAMILY. The fragments are indeterminate angular, seldom slightly rhomboidal. It is translucent, or semi-transparent. It occurs in large and coarse granular concretions, which sometimes approach to the diverging wedge-shaped columnar variety. It scratches glass; and if we draw it very hard over the surface of quartz, it slightly scratches it. It is rather brittle. It is easily frangible. Its powder is rough to the feel. Specific gravity, 2.9257, 3.2, Hmty. 2.832, Karsten. 3.000, Wid. Chemical Characters. Before the blowpipe, it loses its colour and transpa rency, melts with great difficulty, often only on the edges, and with considerable ebullition, into an opaque glass. Constituent Parts. Silica, 27.0 Silica, 35.5 Silica, 52.0 Magnesia, 18.5 Magnesia, 16.5 Magnesia, 12.0 Lime, 21.0 Lime, 16.5 Lime, 20.0 Alumina, 6.0 Carbonic acid Carbon, acid, 12.0 Carbon, acid, 26.0 and Water, 23.0 A trace of iron. Chcnevix. Eucholz. Lomz. Silica, - 50 Magnesia, 25 Lime, - 18 Carbonic acid and Water, 5 Laugicr. Geognostic Situation. Like the asbestous subspecies, it occurs principally in granular limestone, or dolomite, and in metalliferous beds. These beds contain, besides the tremolite, quartz, calca- reous-spar, garnet, blende, galena, copper-pyrites, and vitreous
