Mine Tales: Super-productive mine, long closed, may soon reopen

2014-06-16T00:00:00Z 2014-07-02T16:15:40Z Mine Tales: Super-productive mine, long closed, may soon reopenBy William Ascarza Special to the Arizona Daily Star Arizona Daily Star

The Silver Queen Ledge, near modern-day Superior including the Irene and Hub claims, was discovered in 1871 by prospectors in search of the nearby Silver King Mine.

Known as the Silver Queen Mine, a silver mine that became a renowned copper bonanza, it was renamed the Magma Mine in 1910 after it was purchased for $130,000 by the millionaire mining engineer William Boyce Thompson and his partner George Gunn.

Originally known as Hastings after a San Francisco merchant and miner, Superior was laid out in 1900 by George Lobb and named after Superior, Michigan. That city was home to some of the stockholders of the Lake Superior and Arizona Mining Co. who acquired the nearby Golden Eagle Group of mines previously worked for gold by the Gem Gold Mining Co.

By 1914 the Magma Mine included an ore concentrator. By the summer of 1915 the narrow-gauge Magma Arizona railroad was operating, transporting the mine’s concentrates 35 miles from Superior to Magma, a junction with the Arizona Eastern Railroad nine miles west of Florence. Within a decade it was replaced by a standard-gauge railroad. A smelter was built at Superior in 1924 to improve the mine’s self-sufficiency.

The Magma Mine was the site of one of Arizona’s worst mining disasters. Seven miners lost their lives on Nov. 24, 1927, due to an underground fire that started at a depth of 2,700 feet in the No. 2 shaft.

From 1914 to 1933, the mine produced 355 million pounds of copper. By 1950, the Magma Mining Co. became the eighth-largest copper producer in the United States. At the time, the Magma Mine was the company’s only holding and its value lay in the richness of its ore, which averaged 6 percent copper.

For a time the Newmont Mining Corp. owned a majority of the stock in the Magma Mine, acquiring Magma as a subsidiary in 1969. The Superior smelter was closed in July 1971 because of a strike and costly upgrades necessitated by environmental regulation.

Copper concentrate produced at Superior was sent to San Manuel for processing. However, in 1987 it spun off Magma Mining Co. to its shareholders, allowing it to become an independent copper producer.

Between 1982 and 1990 operations at the Magma Mine were shut down due to high operating costs and low productivity. In 1993 the company was operating three copper mines in Southeastern Arizona including Magma, San Manuel and Pinto Valley.

Although the Magma Mine closed in 1996, there is a project in the works nearby to develop a porphyry copper ore deposit over a mile below the surface where rock temperatures reach 175 degrees.

Active dewatering of the workings (2.6 billion gallons of mine water later treated and recycled for local crop irrigation) by Resolution Copper has allowed for the creation of an exploratory shaft to further study future mine design.

Resolution Copper Mining Co. has offered to swap over 5,300 acres of nearby land to the federal government in exchange for 2,400 acres of viable mining property near Superior. It will employ the underground mining method of panel caving involving blasting the base of the ore body to break up the rock, allowing gravity to channel the ore downward where it will be collected by automated loaders and then shipped for further processing by train.

The mine is projected to inject $61.4 billion into Arizona’s economy over the course of its projected 40-plus year life, producing more than 1 billion pounds of copper per year and meeting 25 percent of U.S. copper demand.

William Ascarza is an archivist, historian and author. Email him at mining@azstarnet.com

Sources: Magma Copper Co., Annual Report for the Year Ended Dec. 31, 1927; “Magma Copper Co.” (1993), “International Directory of Company Histories,” Paula Kepos, editor; M.N. Short, F.W. Galbraith, E.N. Harshman, T.H. Kuhn and Eldred D. Wilson (1943), Geology and Ore Deposits of the Superior Mining Area, Arizona; Volume 1, Environmental Setting and Project Description: General Plan of Operations Resolution Copper Mining (November 2013).

Copyright 2014 Arizona Daily Star. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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