Arizona republican., 1909-07-30
MUCH COPPER.
 IN. SCH|sTS
Geologist Brooks Disproves the Common Prejudice Against Schist Forma- tions of Arizona-Cites Large Copper Deposits.

F. w Brooks, the consulting engineer for the London Arizona and other Ffnney properties, will be of considera- ble interest There is perhaps a pre- judice against the scnists of Arizona The article explains that there is no foundation for this prejudice.
 MT Brooks was formerly geologist for the Arizona Smelling company. which company owned and operated the Humboldt shelter. In 1906 the company commissioned him to make an examination and detailed study uf the geological conditions, ore deposits and the possibilities of successful op- erations throughout the Arizona cop per belt.
 The Santa Fe railroad, through its then alliance with the smelter, had the benefit of these reports And it was MT. Brooks favorable report on the Bill Williams country that called attention to that region and aeeeier- ated the completion of the railroad to Parker.
 The two years spent in working out the geology of the London and Kelvin districts resulted in the organization of the companies which have recently developed some of the greatest cop per deposits in the United States.
 Mir Brooks article follows:
 Those who have watched the growth and development of new mining dis tricts cannot have failed to remark the strong influence exercised by the nature of the rock and structure ac- companying the first discoveries of ore in the further search for new mines. Those localities which do not afford conditions closely resembling the first discoveries are less favorably consid- cred or even entirely ignored. That this is frequently the case where no just basis or ground for prejudice ex- ists, is abundantly proved in the later developments of old established camps. Such, for instance, as the gold discov- cries in the Leadville area and the de- posits of gold ore in the granites of Cripple Creek
 Where such prejudice arises it is well to inquire if it be based upon sound theory, sustained by actual and widespread experiences, or whether, on the other hand, it may not be the re- suit of circumstances of a more or less accidental nature without determining value as criteria. It is in this attitude that I approach the question of Ari- zona schists in their relation to copper mining in the territory.
 That metamorphic schists are favor able for copper deposition is attested by the several large and widely sep arated occurrences, such as Huelva district in Spain; Ducktown, Tennes- see, and elsewhere. Experience there fore is in general favorable to schists.
 UNITED VERDE IN SCHiSTS.
 In Arizona the well known United Verde at Jerome, Yavapai county, is a huge lense in the schist" (so-called Yavapai schist, the local equivalent of the pre- Cambrian Pinal schist of Ran sOme).
 Ransome, in his professional paper Number 12, on the Globe quadrangle, written several years ago, states that although several promising prospects existed at the time in the schist area west of Globe no productive mines had as yet been opened. This, however, he thought might be due to lack of development rather than to the unfav orable character of the formation Since that time, however, the Gibson. Miami and Inspiration have become prominent in this locality, the two for mer having passed from the prospect stage into fully developed mines of great promise.
 As is well known to students of this subject that mineral segregation and concentration into bodies of ore are strongly favored by. periods of move ment and dynamic stresses incident to regional metamorphism, the schists furnish in themselves the best possi- Sle evidence of such shearing, crush ing and intense dynamic alteration and metamorphism as would favor min eral deposition.
 The general conclusions of science are, therefore, favorable to the schists. How comes it then that an acknow- ledged prejudice is entertained on the part of many with regard to the schists of Arizona in relation to de- pOsits of copper ore? -
 1 offer the following explanation for what it may be worth. but in the be- lief that therein lies the crlx of the whole question.
 OutcrOps and surface exposures of copper ores in limestone are more con SpiSuOuS dIlu COnldlI on Jne average, more copper than outcrops and expos ures in schist. This is a mere matter of observation. In limestone the cop per iR the form of bright green and blue carbonates, with some oxides and sulphides, is commonly associated with garnet and related minerals which of fer high resistance to weathering agencies It is accordingly protected from oxidation and removal by leach ing The schists, on the other hand, | readily exfoliate and break down un- der weathering agencies and the re- moval of the copper is easily accom- plished by teaching processes.
 EARLY MISTAKES.
 If this is true, what could be more 1 natural than that the early prospector 1 should give his attention to the rela- lively rich and striking outcrops in the 1 limestone rather than to the less at 1 tractive, although often well defined | veins in the schist with their poor and | lean surface showing. as likely to yield | the quickest results with the least lab | or and expense. Success having once | attended his efforts in the limestone, | a set of conditions became thereby es- tablished to be more or less rigorous ly applied as criteria for further | search. All other conditions of struc-