Mining has played an important part in the history and economy of Pinal County since before it was incorporated in 1875.

The Silver King mine north of Superior was one of the first big producers in the county. 42 million dollars worth of silver were mined from 1875 to 1900. Miners lived in the town of Silver King, and the ore was shipped to the town of Pinal for processing. From there the silver went to Florence for shipment to San Francisco.

silver king town 1885Town of Silver King in 1885

The Mammoth Mine (Mammoth-St. Anthony), a gold mine opened in 1879, closed in 1901 after a cave-in. During World War I, the demand for many minerals rose, and the mine was reopened. For a few years almost the entire molybdenum output of the United States came from this area. The entire Mammoth Mining District effectively shut down at the end of the war. It’s been opened periodically since then, and copper is once again being produced in the area. The Mining District is in southeastern Pinal County.

The Silver Queen mine, near Superior and now known as the Magma mine, produced nugget silver starting in 1875. Like the Mammoth Mine, it closed around the turn of the 20th Century and has periodically been reopened as metal prices have risen.

Mining began around the Ray Mine in northeastern Pinal County around 1880. It was not until the 1920’s, however, that the area started producing any quantities of metal. Copper is by far the greatest commodity that has come from the Ray Mine. Today it is the only large mine still operational in Pinal County.

Since the beginning of mining here, Pinal County has produced over 15 billion pounds (7,500,000 tons) of copper, over 66 million ounces (2062.5 tons) of silver, over 1.5 million ounces (468.75 tons) of gold, and millions of pounds of zinc, lead, and molybdenum.

silver silver king jeff scovil photoSilver, Silver King Mine, Jeff Scovil photograph

There are 47 named metallic mineral districts in Pinal County and hundreds of mines in those districts. Today most of these mines are closed. The Ray Mine is the major producer in the county today. New copper mines are proposed for Superior and Florence, and there are proposals for reopening a mine in Casa Grande.

Map showing metallic mineral districts in Pinal Countypinal mining districts

 

Today there are 544 Pinal County registered mines in Pinal County.

Copper, Silver, Gold, and Lead are the main products coming out of mines in the county. Most of the gold found in Pinal County has been a byproduct of copper mining.

Other commodities produced in Pinal County include Zinc, Manganese, Molybdenum, Silica, Tungsten, Iron, Vanadium, Asbestos, Uranium, Barium-Barite, Fluorine-Fluorite, Semiprecious Gemstones, Quartz, Titanium, Perlite, General Limestone, Mercury, Tellurium, Bismuth, Sulfur, and Beryllium.

Granite, Marble, and volcanic cinders are also quarried in the county.

 

 

 

cross section copper deposit

Diagram showing a typical cross-section of an Arizona copper deposit. The copper is initially deposited as a sulfide in the primary zone. Exposure to air and water causes the copper to go into solution. The surface rocks are leached of copper, but deeper there will be new minerals formed. These are colorful blue and green oxide zone copper minerals like azurite, malachite, chrysocolla and turquoise.

 

There is a mineral named after Pinal County where it was first found. It has only been found in Arizona. It is Pinalite, a lead tungstate chloride (Pb3WO5Cl2). It was found at the Mammoth-St. Anthony Mine in Mammoth. There are not many specimens of this microscopic mineral.

pinalite 2 Brent Thorne

Pinalite, Mammoth, Arizona Brent Thorne specimen and photograph

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