Mohave County miner., 1912-05-04
Miami Copper Company.

inspection to the mine and speaks op,
 tmistically of its future.
 "The 57O-foot level is looking re.
 markedly good, the ore being opened
 up by the development work now in
 progress having a copper content fully
 up to the average for the ore body.
 l have never estimated more than 50
 feet of ore below this level but am confident that it will extend much deeper, and when the time comes a cross-cut will be driven from the main
 shaft on the 720-foot level.
 ''Une xpected ore is being disclosed on the 42O-foot, or present extraction level. On all the levels above, the northern limit of the ore body has
 been determined by an approximately east and west fault but on the 42O foot level drift north through this fault has passed through clean ore for a distance of 100 feet.
 "Seven shrinkage stopes are in vari- ous stages of operation above this level. One is completed and is full of broken ore; mining is being carried on in three of them; and three more are in the preparatory stage. After the stopes are finished and filled with broken ore. the pillars will be remov- ed by top-slicing, at the same time drawing the ore from the stopes so that the capping will settle evenly. Condition may arise that will permit notifications of this method, such as blasting the pillars and weakening them so that they will crush and then drawing off the ore from the stopes and pillars at the same time.
 ''The cost of mining for last year as shown in our annual report was 1.2lS per ton. It might have been 40 cents less if we had desired to mine waste fully and without regard to the safety of the men. The excessive cost was due to the large amount of square, setting and top-slicing that was done around the top and sides of the pre- body for the purpose of forming mat of timber between the capping and the ore. From many years experlence in similar large ore deposits, can un- hesitatingly say that it is absolutely impossible to mine the ore clean and with safety to the miners without placing a timber mat between the ore and the capping.
 "Production is at the rate of not quite 3,OOO,OOO pounds of copper per month but we hope to soon bring it up to that figure. In the concentrator, the Deister tables are doing excellent work but there will be some changes made in the crushing machinery. The Hardnge pebble mills have demonstrated their superiority over the chilean mills for fine grinding and will probably eventually replace them in all units. It is also probable that the rigid rolls used for the inter- mediate crushing will be gradually re- placed by heavy spring rolls in all unlts. The Traylor Engineering Com- pany is building for us an unusually heavy set of spring rolls. They will be of the same size as the spring and rigid rolls now in use, l6 by 42. but will have much more massive frame and heavier construction. Seven Crocker-Wheeler l5Oh. D. motors have been ordered to replace the lOO- h. p. motors now used in driving the rolls. Hardinge ball mills have been tried out against the rolls but have not thus far proved equal to them. Their steel consumption IS apparently great CT than that of the rolls.
 Il do not think that 2O-cent copper will be an event of the near future as some are predicting but can see no reason why it should not hold firm around l6 cents for some time to come. The only possibilities in sight for a large amount of new copper are. the Tanganyika fields in Africa and it will be many years before they will add to the worlds produc- tion. believe the discovery of any more important deposits in this coun. try at least, will be the result of care ful geological work and deep prospect ing. A good business revival will |