Bisbee daily review., 1911-09-05
Mines of Arizona
(By Chas. A. Dinsmorel
oiseoSeries hy olnsmore Alenu the
 sy-ways of the New State

The Mammoth mine al Goldfield Final county, Arizona, is being oper. ated by George T. Young, secretary of state of Arizona. and a 1O-stamp mill IS run 12 hours a day. values save0 III the tails carry about 20 cents per ton only. It is a free milling gold ore, values running from S5 to $50 per ton. A. C. Massey is superintendent: F. w. Cmith. engineer and assaver. F. O. Kennedy, consulting engineer and mill superintendent. Work is be. ing prosecuted through two shafts. to. tai depth being 465 feet.
 This might properly be called disseminated gold porphyry." if one may infringe so much on the popular
 pper expression. Here is a brecciated porphyry, or granite-poTphyry, some. thing more than 800 feet in width. the full length at least of one claim, depth of 400 feet of ore, and through, out the ore runs an average above s. The country is porphyry, trending practically north and south: and there are many flows of andesite running through it. On the Mammoth there are two andesitic flows, between which IS the ore body as stated The andesite is barren. But snere the anGS>tte and brecciatcd materials contact there has beel a concentration of values. wiSb a narrow ore zone of from 2 to 30 feet in width carrying from SIP to S200 per ton in gold. This zone is sharply cut of, by the andesite on one side and by the brecciated material of lesser grade on the other; but from it through the low grade there are many stringers of varying length carrying high grade. In some instances. by following these stringers lenses ot rich ore have been found, but more often this will not be the case. the high grade 'petering out" 10 the reg. ular low grade values The high grade on the contact, however, has it's pc. culiarities. Where the lense is widest the ore is richest, and the Iense is extremely variable in size, widening and narrowing occasionally, and also the high grade zone maintained re liability to the greatest depth at. tained. On the 400 tor Eth as it is called) winze has been sunk 45 feet. and here the bottom is in seO ore, and the indications are that another of the rich shoots or probably the contin. uation of the old one, is coming in.
 To the depth of 100 feet the ore is exactly the same in character and practically so in value as on the sur face. It is all oxidized, no sulphides having been found It was thought that when water was reached the sul- phides would come in, as usual: but it was not the case, so it is altogether probable that this condition will ob tain to much greater depth, and Mir Kennedy states his belief that 1000 feet of vertical depth will find the ore body identical with that at present be- ing worked. Throughout the porphyry there is more or less quartz in angular fragments, giving evidence of consid- erable movement During the past several months much prospecting has been done on the surface and under ground, with in view the definite as- certainment cf quantities of milling ore. It is the belief of those in charge of the enterprise that this property may be worked on much the same principle as that of the Dorphyry cop pers, by caying, after the glory hole" method shall have been abandoned, and for this reason it was necessary to know the quantities. A great many open cuts, shallCw shafts, etc, were made on the surface, drifts and cross cuts and winzes were made under ground, and everything thoroughly sampled and assayed. Taking one full claim, it was all gone over in this manner and aL estimate of the whole made, after which a triangular sec ton was taken, embracing one-half the total area, and estimates made on this, the basis of the calculations being the work done. assays made, depth, width, and length. There are, then, as so ascertained, over 3,000l0OO tons or ore running better/ than s4 per ton fin gold-and in making this estimate all the high grade on the contact was eliminated. There are two more claims on this contact or great body of brec- ciated porphyry which it is reasonable to suppose carry similar values; but as the prospecting and developing of these has been on much more mea- ger scale, no estimate has ever been made as to quantities, etc The mill is running now on old dumps and on waste" which was used to fill the de pleted stopes by the old-timers, anC on ore extracted in development. But the mill is an old one, the stamps very light. and it is the intention to entirely change the milling practice and oper- ate on much larger scale, treating 150 or more tons daily. The new prac- tIce will be to run the ore through gy- ratory crushers, to Chilean mills and thence to cyanide plant. In case, how ever, of the high grade ore. the flow from the Chileans will be by launder oyer plates and thence to cyanide Tests on an elaborate scale have been made on cyaniding this ore. and ex- traction up to @ per cent was made without the addition Of anything, the ore being almost absolutely neutral and easily handled. In fact, the old dumps of tailings from the operation of the mill in the days of the high grade excitement, were purchased some years ago by parties who cyan ided them and made a good deal of money, this being complete demon stration of the feasibility of the pro- cess here. The cyanide tests were made by Mr. Kennedy, and were extensive and thorough, and he ad' vised the installation of the new-style plant as stated; but he strongly ss vised that the plates be used for high
 M.M "a