FOLIATED BROWN BLENDE. 4S1 Variety is opaque. The large and coarse granular varie ties are translucent, sometimes bordering on perfect tran sparent. It yields a yellowish-grey and yellowish-brown streak. It yields pretty easily to the knife. It is brittle. It is easily frangible. Specific gravity, 3.770 to 4.04S, Gellert; 3.963, Kir* won. Constituent Parts. Allonheads, Northum- From Sahlberg. bcrland. ‘Zinc, 44 Zinc, 58.8 Iron, 5 Sulphur, 23.5 Sulphur, 17 Iron, 8.4 Silica, 24 Silica, 7.0 Alumina, 5 Water, 5 97.7 / 100 I)r Thomson. Rergmann, Opusc. t. II. p. 332. Blende, like all other ores, often contains what, chemi- ca % considered, may be viewed as accidental ingredi» ent s; thus the blende of Prizbram frequently contains silver; and that from Nagyag, manganese, lead, arsenic, a °d auriferous silver. Geognostic Situation. It occurs principally in veins and beds, in primitive an d transition rocks ; seldomer in floetz rocks. It is as sociated with ores of different kinds, such as galena or lead-