August 2009

Economic Geology

Butte, Montana (Part 4)

By R. J. Cathro

“Reno Sales insisted that every mine operator, geologist, and even prospector appraises the future of mining properties on the basis of a theory of ore deposition whether he realizes the fact or not, and wherever the ultimate value of a mine or prospect is dependant on undeveloped ore, any estimate by an engineer or a geologist necessarily involves a theory of the origin of the deposit. Thus, the importance of a theory of the genesis of ore deposits cannot be overestimated”

~ Perry and Meyer, 1968

Mine mapping

Because of its economic importance, the litigation problems caused by the Apex Law, and its extensive underground development (1,600 kilometres of drifts and 67 kilometres of shafts), Butte received more intensive study than almost any other mineral deposit, which is why it ranks as one of the most important sites of mineral deposit research.

According to Graton (1947), Anaconda’s Butte mines hosted “the first geological department of any importance established by a mining company — and perhaps the earliest on any scale.” He described its origins as follows:

“Systematic study of the Butte deposits by the U.S. Geological Survey had begun in 1896 under the direction of S.F. Emmons and continued for several years. … D.W. Brunton, as consulting engineer for Anaconda, advocated geological study (to resolve boundary disputes arising from the Apex Law) in 1900 and engaged for that purpose H.V. Winchell, who organized a staff and began systematic underground mapping. … In 1901, R.H. Sales, who had earlier worked (in other Butte mines and with the Federal geologists), joined the company’s geological department. In 1906, Sales became chief geologist.”

Reno Sales was born in Iowa in 1876 and moved to Bozeman, Montana, in 1881 where his father became a rancher. After receiving a science degree from Montana State College and a graduate degree (Engineer of Mines) from Columbia School of Mines in 1900, he returned to Montana to become an engineer-surveyor at Butte. Sales, Winchell and Brunton began to standardize and compile the geology throughout the camp and, in the process, they established the principals for systematic surface and underground mapping that eventually became the model used worldwide. This was the same Brunton who had received a patent in 1894 for the compass that is named after him, and which is still in use. Sales served as chief geologist until 1948, another 14 years as a consulting geologist, and died in Bozeman in 1969 at the age of 92.

In its early years, Anaconda’s geological work remained closely concerned with boundary rights and litigation. The underground mapping was, therefore, carried out with unprecedented care and detail to make the maps, sections and models express the exact conditions underground and to ensure that they would be difficult to challenge in court. Since Butte is characterized by numerous strong, through-going veins of various attitudes and by several sets of strong fault displacements, and because Apex litigation primarily involved geometrical considerations, the geological work of those early years was concerned chiefly with the interpretation and solution of structural problems.

After the ownership of the mines was consolidated and the litigation period ended, the geological department began to focus more on geological features on a district-wide basis. Initially, priority was accorded to mine operation and production. In particular, great efficiency was achieved in projecting the known pattern of intersecting veins and faults into contiguous unopened ground. In addition, the nature and geometry of the mineralization received consistent attention, and variations in mineral character and texture and in the type and intensity of wall-rock alteration gradually evolved into the well-known zonal pattern. In 1913, Sales published a classic paper on mineral zoning at Butte that stands as one of the great geological contributions made directly by a mining company.

In 1919, the geological department took over the direction of mine sampling; it was combined with the mining department in 1928 to form a group that employed 15 geologists, 44 engineers, 67 samplers and 11 draftsmen. At the same time, a new program was implemented to develop a new tonne of ore reserves to replace each tonne mined (Linforth, 1933). The Butte geological department was the largest and strongest of its kind for many years and was credited with training a large number of geologists in standardized and effective methods of underground mapping (the Anaconda school). One unique policy was that responsibility for underground exploration was steadily delegated to the geological department, rather than to the production department as at most mines. That policy is still resisted at some mines today.

The three basic contributions of Reno Sales to mining geology were described as follows: 1) he provided a superb standard of technical competence and intellectual integrity at a time when others were confusing observations and ‘authority’; 2) few men, within the universities or outside, directly and personally influenced as many students of mining geology (nearly 100); and 3) he left us with a basic philosophy, endeavouring throughout his life to minimize the distinction between pure and applied geology (Perry & Meyer, 1968).

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