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Contributed by Arizona Geological Survey
Since February 1863, when President Abraham Lincoln first recognized the Territory of Arizona as a protectorate of the United States of America, mining has been the backbone of the Arizona economy. And for over a century, the Arizona Geological Survey and its predecessors have collected and archived information on mines and mine activities in Arizona.
The Mines Collection of the Arizona Geological Survey contains information on thousands of Arizona mines - only a select few are displayed here. All told, the collection comprises more than 82 linear feet of files filled with old newspaper clippings, accounts of mine histories, geologic reports, mineral assessments, production reports, historic letters inquiring of ore reserves and economic viability, and to a lesser extent, maps, geologic cross-sections, assay reports, mine schematics, and photographs. Most of the files were compiled between 1900 and 1960. These files shine a light into individual mines, which, when taken collectively, illuminate the rich and diverse history of mining and miners in Arizona.
The earliest miners were prehistoric Native Americans who harvested outcrops of salt, clays, hematite, quartz, obsidian, stone, turquoise, and coal. In the late 1600's, Spanish explorers began the hunt for metallic deposits with especial focus on gold and silver. In 1854, in Ajo, Arizona, the Arizona Mining and Trading Company launched the modern era of hard-rock mining.
A burgeoning mining industry fostered growth in the Arizona Territory, and by 1864 nearly 25 percent of the male, non-native populace was made up of prospectors. By the 1870's, an uptick in hardrock mining yielded prodigious volumes of copper, lead, zinc, silver and gold ore. In 1912, the newly christened state of Arizona supported 445 active mines, 72 concentrating facilities, and 11 smelters; their gross value that year was nearly 67 million dollars - equivalent to 1.4 billion dollars in 2006.
And here at the start of the 21st Century, the important metallic commodities of Arizona -listed in order of decreasing value - include copper, gold, silver, molybdenum, and lead. Important non-metallic (industrial) minerals - listed in order of decreasing value - include sand and gravel, crushed stone, clay, cement, gypsum, lime, perlite, pumice, and salt. Arizona's is world-famous for its turquoise, peridot, petrified wood, and for striking, copper-bearing minerals: turquoise, azurite, malachite. Energy resources of Arizona include coal and small quantities of petroleum and natural gas.
But copper is king! In 2007, Arizona's copper mines produced more than 750,000 tons of copper with a value of 5.5 billion dollars. Most of the copper mined in Arizona stems from porphyry-copper deposits, which are associated with intrusive igneous rocks similar to granite. The term porphyry describes the typical texture of these rocks, in which individual mineral grains, from about one-tenth inch to a half-inch in size, are fixed in a matrix of smaller grains that are barely visible to the naked eye. Other minerals common to copper porphyry deposits are molybdenum and silver.