WACKE, 85 It feels rather greasy. Specific gravity, 2.617, 2.887, Kirwan. 2.790, Ear* ften. Chemical Character. Before the blowpipe, it melts into a greenish slag. Constituent Parts. Silica, - 63.00 Alumina, - - 13.00 Lime, - - - 7.00 Iron, - - - 17.00 Withering, The above analysis is of amygdaloid, not of pure wacke t so that an analysis of that substance, in its unmixed and characteristic form, is still wanting. Geognostic Situation. It occurs in transition mountains, in the form of amyg daloid t in flcetz mountains, either in the pure state, or in the amygdaloidal form, in beds, mountain-masses, and I'eins, generally associated with basalt. Geographic Situation. It is a frequent rock, either in the pure or amygaloidal form, in the different districts in Scotland where basalt occurs; and on the Continent of Europe, it also occurs in basaltic countries. . Observations. ^ % r 1 • Its colour, streak, and inferior hardness, distinguish it from Basalt. * ' y 3 s. it