496 MINING INDUSTRY. 



vein are usually pretty well defined, the south wall more especially so. This 

 is almost always easily followed and presents the ordinary features of the wall 

 of a true fissure vein. A thin clay selvage, or parting, between the wall and 

 filling of the vein, is apparent in most places. The north wall seems to be 

 less regular, and, in some parts, is difficult to distinguish. The filHng of the 

 vein is a quartzose and feldspathic mixture, highly siliceous, and carrying much 

 free quartz, but not having the usual characteristic appearance of solid quartz 

 veins. In many places even where the vein is wide and well-defined, the 

 filling of the fissure has a granitic look, differing but little in appearance from 

 the country-rock, and usually, in such cases, it is quite as barren. The gangue 

 accompanying the ore is a soft, whitish, or pale-greenish rock, consisting 

 chiefly of decomposed or altered feldspathic material, mixed with quartz, and 

 thickly impregnated with iron and copper pyrites, usually in small crystals. 

 The richer ore is concentrated in a seam of solid sulphurets, consisting mainly 

 of iron and copper pyrites, intimately mingled with which are comparatively 

 small quantities of galena, zincblende, arsenical pyrites, and other allied min- 

 erals. The precious metals, chiefly gold, but rarely, if ever, entirely without 

 silver, are associated with the pyrites. Usually the fine copper pyrites is the 

 richest source of gold ; the iron pyrites, when fine and close-grained, is also 

 a rich gold-bearing ore, but when coarse-grained and crystalline it is much 

 lower in value. 



The productive portions of the vein usually carry a seam of the solid, 

 gold-bearing pyrites, varying in width from an inch or two to two or three 

 feet. An average width of ten or twelve inches is deemed an excellent vein 

 of pay-ore. This seam of pyrites is usually accompanied by a mass of vein- 

 matter or gangue, from one to three or four feet in width, which carries the 

 finely-crystallized sulphurets, generally disseminated through it, as already 

 described. These two methods of occurrence of the ore furnish two quali- 

 ties for treatment ; the last named, that which fills the greater part of the 

 vein, affording stamp-rock that yields about an ounce of retorted amalgam, or 

 $16 50 to $18, coin, per ton; the former, or the concentrated seam of py- 

 rites, affording the first-class or smelting ore, assaying from three to twelve, 

 and averaging about six ounces of fine gold and six ounces of fine silver per 

 ton, besides the copper, which, when saved in the smelting process, forms an 

 important element of its value. 



