YELLOW BLENDE. 427 Vviiich passes, on the one side, into grass-green, aspara gus-green, oil-green, and olive-green ; on the other, into hyacinth-red, aurora-red, brownish red, even into red dish and yellowish-brown. All these colours incline toore or less to green. It occurs usually massive, disseminated, and crystalli sed, in several of the forms exhibited by brown-blende. The crystals are middle-sized and small, but usually so touch grown together, that it is difficult to determine their figure. The crystals have a smooth surface. Externally and internally it is shining and splendent, and the lustre is adamantine. The fracture is more or less perfect and straight folia ted, with a sixfold cleavage. The fragments are dodecahedral, but on account of the distinct concretions can seldom be obtained perfect, and ar e therefore most commonly indeterminate angular, and s harpedged. It occurs in distinct concretions, which are large and eoarse, but seldom small granular. It is usually only translucent, but the lighter coloured Varieties are semitransparent, inclining to transparent. It is duplicating translucent. It yields a yellowish grey or yellowish-white streak. It yields pretty easily to the knite. It is brittle. It is easily frangible. It is heavy. Specific gravity, 4.044 to 4.048, Gtllert; 4.067, Kir- Wan >' 4.103, Karsten. Physical