Bisbee daily review., 1904-02-28

Below is presented the third paper
 by F. L. Ransome, on the geology and ! copper deposits of Bisbee. Arizona. the
 preceding papers having appeared in
 The Daily Review of February 13 and February 21:
 Written by F. L. Ransome, fer the l Mining and Scientific American)
 Neurological Character of the Ores The ores worked by the Copper
 Queen Consolidated Mining company
 up to 1893 were oxidized ores
 consisting chiefly of malachite
 azurite, cuprite and native copper In the upper levels the malachite and azurite occurred as beautiful incrus-
 tations and stalactites lining caves in
 the limestopes. These "cave ores' have been exhausted. and although
 oxidized ore is still abundant. it occurs generally as soft earthy masses, often containing curite and native copper, and usually associated with large amounts of limonite and kaolin. Ma. tive copper and crystalline cuprite are still abundant in the recently opened worings of the Calumet 6 Ari. zona mine.
 The original sulphi6e ores, from which the oxidiZed ores have been de rived. consist of pyrite containing va riable amounts of chalcopyrite and sometimes a little sphalerite. These pyritic ores are sometimes directly in contact with oxidized ores, but it is
 cocite between the two. The min
 eral, familiarly known as copper
 glance" or glance" is the most i'm
 Hortant sulphide occurring in the Bis
 bee quad rangle. since nearly all of the
 bodies of workable sulphide ore owe
 their value to its presence. So far
 IS observed. it occurs only in massive form. distinct crystals being nowhere seen. It is sometimes firm and com
 ract in texture, but is often rather
 soft and occasionally has almost a
 sooty character.
 The chalcocite occurs at various
 depths, but nowhere far from ore
 showing at least partial oxidation. Its most characteristic place of occur renee is in the irregular zones of rich sulphide ore that usually intervene be-
 tween masses of lean pyrite and OK ifi7.od ores containing rnDrire native copper and carbonates. The ore of these zones often consists of soft crumbling pyrite, which is intimately associated with dull. crypto-crystal- line chalcocite in the form of a thin envelope about the pyrite grains. The greatest depth at which chalcocite has been observed is 1050 feet. in the Cal umet & Arizona mine Bornite has been reported from some Of the ere bodies, but arsenical or antim onia compounds of copper are absent, 90 far as known. The copper bearing minerals of the oxidized ores include malachite. azurite, chrysocolla. mel anochalcite, aurichalcite. brochantite cuprite, tenorite and footeite.
 Of the various gangue minerals as- sociated with ores, calcite, in it's role of principal constituent of the lime stone in which the important ore bod ies occur. is the most abundant It is seldom. however. that the mineral limestone in the immediate vicinity of the ore as it does of the un- changed rock in which naturalization has not been active. It has largely been replaced in the process of miner alization by pyrite, amphibole, pyrox- enc, garnet, chlorite, quartz, vesuvi- anite and other minerals. The re- sulting rock is usually of more com pact texture than the unaltered lime stone and is slightly greenish in tint The metamorphic silicates are, as a rule. recognizable cnly under the mi croscope, and the contact metamor phism is therefore very inconspicu ous as compared with the altered limestones of the Cananea district to the south.
 Genesis of the Ore Deposits.-Two general processes have operated to form the ores now exploited. These are CD metasomafic alteration, in- cluding pyritic naturalization. and (2) oxidation and its attendant phe- nomena of transportation and enrich nent Concerning the. precise boun- iary between these two general ac- .ivities some difference of opinion is possible; but as regards the essential share of each in the genesis of the pres there can be no question. There are few known ore bodies in the Bis bee quadrange which do not demon strably owe their value to the CO operation of both processes. This was also the conclusion reached, by Emmons from the descriptions of Douglas and from a brief visit to the Copper Queen mine. The existence of workable masses of ore that have resulted wholly from the primary met