86 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



(2) Vein rock, amygdaloid witli medium-sized amygdnles, mostly filled with cal- 

 cite, but coutaiuing a few streaks of copper. Characteristic sample of promising 

 rock taken 4 feet from hanging wall. (54285.) 



From 60 feet below the tenth level, where the shaft is under the vein : 



Characteristic sample of the foot wall taken 20 feet from the hanging wall. 



(.54252.) 



In prospecting from the conglomerate into the overlying trap, a 

 series of apparently isolated irregular bodies of cupriferous amygda- 

 ioids were discovered, and this series has been called the West vein. 

 To illustrate this vein the following specimens are shown : 



(1) Trap, containing a few good sized amygdnles filled with a dark-green min- 

 eral. Represents the hanging wall of the conglomerate. (54288.) 



(2) Amygdaloid, 12 feet in the cross-cut. (54286.) 



(3) Trap rock, 20 feet in the cross-cut. (.54284.) 



(4) Amygdaloid, 70 feet in the cross-cut. (54271.) 



(5) Amygdaloid, 100 feet in the cross-cut. (54292.) 



(6) Trap, 100 feet in the cross-cut, showing some thin flakes of copper. (.54287.) 



(7) Barren amygdaloid, 120 feet in the cross-cut. (.54317.) 



(8) Ore, amygdaloid coutaiuing considerable branching copper, 120 feet in the 

 cross-cut. (54299.) 



(9) Two characteristic samples of the West vein ore taken from the rock house. 

 (54290 and 54295.) 



THE SEPARATIOX OF THE COPPER FROM THE ROCK. 



After passing the final screen at the rock house, the ore is delivered 

 to the stamx) mill for further treatment. As delivered to the mill, the 

 ore contains copper in very small masses, threads, sheets, and amyg- 

 dnles, from microscopic size up. 



The object of the treatment in the stamp mill is, first, to crush the 

 ore so as to liberate the copper from the inclosing rock material, and then 

 to separate the copper from the rock by jigging in running water. The 

 fineness of the crushing is governed by the fineness of the copper, and 

 in general the finer the crushing the more perfectly is the copper liber- 

 ated from the rock ; on the other hand, the fine crushing tends to flatten 

 the coarser copper into thin sheets, which are very difficult to catch on 

 the jigs, so that the crushing is never carried far enough to liberate all 

 of the copper. 



Particles of rock containing copper are always found on top of the bed 

 of the coarse copper on the sieves, since they are too heavy to be carried 

 away by the current of water, and yet not heavy enough to settle well, 

 and too large to pass through the sieve. This material is removed sep- 

 arately, and is called "ragging." It is sometimes returned to the stamps, 

 and is sometimes treated in special apparatus. 



The crushing takes place in large stamps, which are constructed so 

 as to deliver a blow by the expansion of steam on the same general 

 principle as a steam hammer ; but this application has somewhat altered 

 the construction, and it has been so improved that a single stamp will 

 crnsli about 200 tons of rock in 24 hours so as to pass a screen with 

 holes three-sixteenths of an inch in diameter, placed in the front and 



