Volltext Seite (XML)
OBSlDIAtf. £71 times passes on the one side into greyish-black, ash-grey* & nd smoke-grey, and on the other into pitch-black. The colour is generally uniform, seldom spotted or striped. Iu some varieties (those from South America) a pinch beck-brown light is to be observed. It occurs massive, in blunt-cornered pieces, and some times in original grains, which are angular or roundish. The external surface of the blunt-cornered pieces is r °ugh ; that of the grains sometimes rough, sometimes smooth. Internally it is.specular splendent, seldom shining, and tbe lustre is vitreous. The fracture is perfect, large, and rather flat conchoi- dal. It breaks into angular and very sharp-edged fragments, "’hich sometimes incline to the tabular form. It alternates from translucent to translucent 011 the C( lges. It is hard. It is very brittle. It is easily frangible. Hatlier heavy, in a low degree. Specific gravity, Peruvian, 2.318, linsson. Icelandic* -38.2, 2.397, Iloff. Hungarian, 2.371, 2.358, Hoff. Chemical Characters. I be black obsidian of Iceland, according to Da Ctf- rnara , on charcoal, before the blowpipe, melts into a pale as h-grey imperfect vesicular glass. The obsidian of . le ^ at ’d of Candia, before the blowpipe, was changed r?,!° a "bite, light, and uncommonly porous mass. 'at of Spanish America, before the blowpipe, lost black colour, became white, spongy, and fibrous, I1( I increased to seven or eight times its original bulk: