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COMMON JASPER. Internally it varies, according to the fracture, from shining to dull; and the lustre is resino-vitreous. The fracture of some varieties is more or less perfect and flat conchoidal, and these have a shining or glistening lustre : in others it is even, with a glimmering lustre, or fine earthy and dull. The fragments are angular, and more or less sharp edged. It is opaque, or very faintly translucent on the edges. It is hard in a low degree. Rather easily frangible. Specific gravity, 2.554, 2.1)71, Ilaherle. 2.580,2.700, Kirwan. 2.298, 2.314, 2.349, 2.573, 2.665, Hoffmann. Chemical Characters. It is infusible without addition before the blowpipe. It retains its colour for a considerable time, and at length becomes white. Gcorrnostic Situation. O It occurs principally in veins, as a constituent part of agates, or in imbedded cotemporaneous masses in primi tive, transition, and floctz rocks. The veins in which it occurs are either entirely filled with jasper, or they con tain also ores of different kinds, as of iron, lead, or sil ver. It is found more abundantly in ironstone veins than in those of lead and silver; and the iron ores with which it is associated, are red and brown ironstone, accompa nied with quartz and iron-flint. The lead ores are lead- glance; and the argentiferous minerals are native silver, and vitreous silver-ore. The most beautiful varieties, and the largest masses, occur in veins entirely filled with jasper, or a mixture of jasper and agate. R 3 Geographic
