Commonwealth Mine, Pearce Arizona

Commonwealth Mine

Ok, all the other mines listed are in the Dragoon Mining District. This mine is little more than a dozen miles directly southeast of Golden Rule Mine but was not only intricately tied to the Dragoon Mining District but was a significant Arizona producer. So much so that if you can get your hands on an 1897s Morgan Silver Dollar, there is a 1 in 3 chance it was made from silver from the Commonwealth Mine. They increased ingot size to 900 pounds to discourage theft and shipped them directly to the US mint in San Francisco, according to Clive Bailey, Dragoon resident, geologist and local mining historian.

Its historical production of metals was reportedly to be 1,341,000 tons of ore yielding 126 tons of copper, 8 tons of lead, about 138,000 ounces of silver and more than 12,000 ounces of gold. Production was from 1895 to the 1940's, with fluorite being produced until 1971. It is still being mined today.

There were 5.8 million 1897 S Morgan Silver Dollars minted.

So as a salute to the Commonwealth mine and the role it played in our local mining success, it's getting a page here on DragoonArizona.com

Image credit: https://www.pcgs.com/coinfacts/coin/1897-s-1/images/7250

Commonwealth Mine Summary: February 2024
by: Clive Bailey, Geologist former Mine Manager from 1994-6

February 1895 John Pearce climbed the hill to scan the valley for livestock. Absent-mindedly broke a "nubin" off a quartz ledge. The rock assayed 1100
oz silver &; 1/2 ounce gold per ton.
Commonwealth Mining & Milling the new company bought out the Pearce family. Work began Jan. 3 1896 The ore body was 6'-20' wide with ore
running $40-$130 per ton. (1896 price Gold @ $20.67/oz Silver @ $.54/oz)
1897 a 20 stamp mill was imported from New Mexico & Two 50 ton German ball mills were added. The mill went into production September 1,
1897 120 tons/ day producing a 1,000 lbs of bullion cast into 180lb ingots, freighted to Cochise Station and shipped by rail to the San Francisco Mint.
1897-8 The Commonwealth Produced $75,000 a month in bullion.
Spring 1899 new equipment 30 stamps, engine, six large boilers and Steam hoist.
June 17, 1900 disaster struck fire destroyed much of the Commonwealth mine buildings.
The night of April 22,1904 the Pearce town burns. Lack of water hindered firefighting efforts.
1909 the mine had produced $10 million in gold & silver.
March 23, 1910 fire destroys mine mill and equipment again.
1913 the "D" is sunk to the 8th level. 200 men were on the payroll. The war in Europe causes the silver price to fall.
Between 1917-1927 commonwealth averaged fifty to seventy cars a month 115,000 tons of 12.5 oz silver and 0.10 oz gold.
In the "D" Shaft - Water was at the 7th level, mining on the 8th required pumps which could hardly keep up. Results from our 1996 Harvest Gold
drilling indicates a static water level drop of over 130 since 1930.
The Mine had a good run: producing 1.3 million tons of ore yielding 138,000 oz silver & 12,000 oz of gold.
Added Source info: "The Dragoon Mountains" book by Lynn R. Bailey 2008

Description from : https://www.mindat.org/loc-10260.html

A former underground Ag-Au-Mo-Cu-Pb-V-Silica mine located in the NE¼ sec. 5, T.18S., R.25E, 1/2 mile E of Pearce, on private land. Discovered by John Pearce in 1895. Produced 1895-1979. One of Arizona's major silver producers. Owned at times, or in part, by the C.O.R. Ford Corp. of Dallas, TX (1979); Commonwealth Mining and Milling Co.; Montana Tonopah Mining & Milling Co.; and the Commonwealth Development Co. Operated by GOURMET CHIEF INC. (1975). Additional names associated with this mine: Main Mine, North Mine, Hartery veins, Footwall Mine, Discovery stope.

Mineralization is irregular silver-gold halides and minor sulfo-salts with some manganese in quartz-calcite fissure veins and in fault breccia zones (on the hanging wall) in silicified Tertiary rhyolite and andesite volcanics. The ore zone is 1,219.2 meters long, 106.68 meters wide, depth to bottom of 152.4 meters, and 18.29 meters thick, striking N-S (main vein), and dipping 60E. Alteration is propylitic, silicification, and oxidation. It is more intense in and near vein fractures. Sericitic and K-feldspar alteration exists closest to the veins, with extensive argillic and propylitic alteration away from the veins. The associated rock units are the Pearce volcanics and the Brockman Andesite.

Local structures include volcanic flows that dip 35-40E. Fissure veins and fault breccia zones; N-S faults are pre-mineralization, others are post-mineralization.

Workings include a shaft(s). Two inclined shafts, 62 degrees, with extensive workings on 8 levels. The water level was at 700 feet, and a majority of mining was done above the water table, although shaft "C" was eventually sunk to 1,000 feet. There are about 20 miles of underground workings. The workings are 9,144 meters long in total and 152.4 meters deep. Over 1,000,000 tons of ore were produced from 1895 to 1942. Tailings being reworked, 1976-19, flotation methods. Intermittent shipments of tailings were made in the mid-1980'S. About 100,000 tons of tailings had been sold for use as high-silica smelter flux. It is estimated that up to a million tons of tailings remained. In addition, there are approximately 150,000 tons of mine dump material in the area that average 2.5 oz of Ag/t.