352 MiNma industey. 



running north and south, there prevails a zone, more favored than the rest, 

 within the Hmits of which the northwest and southeast veins traversing it are 

 especially rich in ores of high Value, and beyond which the proportion of base 

 metals is greatly increased. This zone, so far as understood, also has a north 

 and south direction. On Lander Hill it may be from a quarter to a half mile 

 in width. Its western limit is thought to pass through the Diana and the 

 Savage mines, so that in passing from the southeastern to the northwestern 

 portions of those claims a perceptible diminution of the richer and purer sil- 

 ver-bearing minerals, and an increasing predominance of baser metals, such as 

 lead, zinc, copper, antimony, and iron, take place. Proceeding still further 

 west the proportion of rich silver minerals to the baser compounds becomes 

 still less, until the ore is quite too poor to pay for extraction. 



It is within this "rich zone" that are situated the working and producing 

 mines of the present day, for only those mines that produce rich ores can 

 afford to work under existing conditions. As will be shown further on, the 

 costs of mining in small veins, in which the ore is not uniformly distributed, 

 are very great, because to obtain one ton of ore, many tons of worthless rock 

 must be mined; in addition to which the costs of metallurgical treatment are 

 also great. In the " rich zone," as well as in the poorer zone, are many 

 mines cajDable of producing low-grade ores, whose development must wait 

 until means of concentration of such ores are introduced, or cheaper methods 

 of treatment are made practicable. 



NoETH Star Vein. — Probably the most important vein of Lander Hill, 

 judging by developments thus far made, is that known as the North Star, on 

 which are located the mines of the Buel North Star, the Manhattan, and the 

 Timoke. The outcrop of this vein is on the south slope of the hill. It has a 

 general direction of northwest and southeast, dipping, under the hill, or to the 

 northeast, at an angle varying between 20 and 30 degrees; but both course and 

 dip are very irregular, owing to the broken condition of the ground and the many 

 faults and displacements of portions of the vein, that are the results of frequent 

 movements of the inclosing rock. Like the other veins of Lander Hill, it is 

 inclosed in granite. The walls are generally well defined, usually carrying a 

 selvage, or gouge, of clay on either side of the vein. In some places the seam .* 



of clay is wanting, but the wall-rock, in the vicinity of the vein, is much de- ^ 



I 



