The geology of the Chance Mine, located in the northeastern portion of the Swisshelm Mountains about 30 miles north of Douglas, consists of a hydrothermal deposit, limestone formation with andesite intrusive, granite and alluvial deposits.
Named for John Swisshelm, who surveyed the Swisshelm district in the latter 19th century, the mountains — notably Swisshelm Peak at 7,183 feet — served as a heliograph station for Gen. Nelson Miles during his campaign against the Apaches in 1886.
Several prominent mines in the locality include the Mountain Queen and the Chance, discovered in 1885 by John Scribner, a Tombstone prospector.
Jacob Sherrer, a sawmill operator in the Chiricahua Mountains, also located claims encompassing the Chance group.
R.N. Reynolds, who in 1913 leased the Mountain Queen, is said to have profited by $1 million off his Chance Mine ventures through 1926, though this may be speculative.
Mineral commodities produced by the Chance Mine included lead, silver, gold, copper, zinc and calcium limestone.
Further studies revealed 3,000 tons of vanadium found in the mine and the dumps.
The Colford Copper Co. attempted to mill vanadium ore on-site while shipping limited quantities of lead-silver ore. It successfully put in a steam hoist around 1911. Early production involved small shipments of oxidized ore by wagon to Webb, a station several miles north of Elfrida along the Douglas-Courtland branch of the El Paso and Southwestern Railroad.
Operation and production of mines in the Swisshelm district was intermittent and has remained so to the present.
By 1935, serious development occurred at the site upon the discovery of ore on the Mountain Queen claim at a depth of 116 feet.
A drift from the Chance No. 1 claim was run to the Mountain Queen claim, connecting both.
Milling equipment included four gasoline engines, a crusher, rolls, screens and a concentrating table producing one ton of ore per hour. A hoist powered by an eight-horsepower engine, an elevator, 1,500 feet of track along with three mine cars and a blacksmith shop also existed at the site, with water for the small milling operation coming from a nearby 140-foot shaft.
However, in 1941, a cave-in forced a halt to operations conducted by lessee Ether Hayne. Between 1939 and 1941, the mine reportedly produced $80,000 worth of ore.
Funded by the Reconstruction Finance Corp., mining resumed at the site by lessees R. L. Brown and the Rydbom brothers during the late 1940s.
Ore was removed and trucked to Douglas, where it was sent by rail to the El Paso smelter. A new shaft was sunk at 250 feet in depth connecting with an ore body at 200 feet. Several drifts and cross-cuts amounted to an additional 1,000 feet. Production of 3,500 tons, valued at $140,000, occurred by 1951.
The average grade of the ore per ton included 25 percent lead, 28 ounces of silver and 0.2 of an ounce of gold.
The Swisshelm Mountain Gold and Silver Mining Co., incorporated by Ben Heney of Tucson, operated a four-man crew on several nearby claims including the N. Mammoth and N. Whale in 1947. Mineralization in the mine included some gold and silver found in stopes on the first level.
In the 1960s, exploration in the form of geophysical analysis and diamond drilling was undertaken by the Anaconda Co., J.F. Rydbom, Hudson Bay, the Phelps Dodge Corp. and others.
Induced polarization was carried out at the site then leased by Daniel L.E. Huckins in December of 1964 by the Heinrichs Geoexploration Co. Subsurface information to a depth in excess of 250 feet was obtained, revealing ore body localities including massive sulfide mineralization confirmed later by diamond drilling.
By 1967, the Chance shaft had been retimbered down to 100 feet and a steel headframe was erected on site then operated by Rydbom and Huckins.
Rydbom maintained a residence near the mine site. The mine was shut down in the early 1980s due to litigation, lack of capital and defined profitable ore reserves.
