68 



MINERALS AND GEOLOGY 



and in combination of the cube and octahedron (fig. 37), and other 

 related forms : also in irregular masses, 

 mostly with well-marked lamellar struc- 

 ture. Cleavage cubical and easily effect- 

 ed. H = 2.5 ; sp.gr. 7.2 7.7. BB, 

 decrepitates (as a general rule) and be- 

 comes reduced to metallic lead. The 



charcoal is entrusted partly with a yellow ring of lead oxide, and 

 beyond this, with a white deposit of mixed sulphate and carbonate 

 of lead. 100 parts of galena contain: sulphur 13.4, lead 8G.6 ; but a 

 minute portion of the sulphide of lead is almost invariably replaced 

 by sulphide of silver. In most Canadian samples however, the 

 amount of silver does not exceed ten or twelve dwts. in the ton, and 

 is consequently insufficient to defray the cost of extraction. The 

 known or reported exceptions to this statement are mentioned be- 

 low. 



Galena, as a mineral, is very widely distributed throughout Canada : 

 both in veins, and in small crystalline masses, &c., scattered through 

 rocks of various kinds, more especially in metamorphic and other 

 limestones or dolomites. It is thus present in almost every mineral 

 vein on the north shore of Lake Superior, in association with zinc- 

 blende, copper and iron pyrites, &c. Also, here and there, through- 

 out the wide Laurentian area between the northern lakes, and the 

 Ottawa ; in the limestones and dolomites of the Niagara and other 

 formations in Ontario ; in the dark calcareous shales around Quebec ;. 

 in the metamorphic region of the Eastern Townships ; and in the 

 limestones of Gaspe. Some of the more special localities comprise : 

 Prince's Location, Lake Superior ; the silver vein of Thunder Bay 

 and Thunder Cape; many veins holding copper pyrites, ifec., north of 

 Thunder Bay ; the region around Black Bay, where it is associated 

 with auriferous copper-pyrites in broad veins;* the district north of 

 Garden River, between Lake Superior and Lake Huron, where it 

 holds a considerable amount of silver ; in well-defined veins of much 



* A surface-sample obtained personally from a quartzose vein in the Upper Copper bearing 

 rocks of this district, gave me : 47.56 per cent, metallic lead, 8.10 per cent, metallic copper 

 (another sample gave 11.62 per cent.), with an amount of gold equivalent to 16 dwts. 18 grs. per 

 ton of 2000 Ibs. of ore, and 2 oz. ]2 dwts. of silver. The amount of gold in different samples 

 varied from 14 to 19 dwts. per ton. according to the amount of pyrites. This vein is about 

 10 feet wide, and carries in its centre a solid lode at least 4 feet in width, of a mixture of 

 copper pyrites and galena. 





