The Butte Mining District Of Montana

Author : Eugene S. Perry
Publisher : Forgotten Books
ISBN 13 : 9780366255320
Total Pages : 44 pages
Book Rating : 4.2/5 (553 download)

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Download or read book The Butte Mining District Montana (Classic Reprint) written by Eugene S. Perry and published by Forgotten Books. This book was released on 2018-04-28 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from The Butte Mining District Montana Although the Butte district, greatest of all copper camps, has produced more than worth of copper, it has also yielded one-fourth of that amount in silver, zinc, gold, and lead. Development in this district began with placer-gold mining in 1864; 20 years later the oxidized silver ores were mined; since 1881 copper has been the chief product. The ore deposits, in part fissure fillings but mainly replacement veins, are confined to granite and aplite in the Boulder batholith, which was intruded in late Cretaceous or early Tertiary time. Three main systems of fissures - early, intermediate, and late - cut the granite in three directions. The first and second are mineralized; the second and third are conspicuous fault fissures. The copper minerals are chiefly primary chalcocite and bornite, with considerable enargite. Sphalerite, galena, native gold, native silver, and silver-bearing tetrahedrite are other valuable minerals. The ores of the district show a well marked zonal arrangement, copper minerals form a central core; copper and zinc minerals an intermediate zone; and zinc, lead, and manganese minerals a peripheral zone. Oxidized copper, zinc, and lead minerals have always been inconspicuous, but oxidized silver minerals were formerly mined. Superficial alteration has affected the deposits near the surface, resulting in thorough leaching to a depth of 100 to 500 feet (30 to 152 meters) and in the deposition of secondary sooty chalcoc1te for 100 to 500 feet below the leached zone. The main mass of ore extending from a depth of 500 feet to more than 4 000 feet meters) 18 believed to be of primary origin and to have been deposited by ascending magmatic solutions under conditions of intermediate thermal intensity. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.