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Iron Cap Mine, Old Dominion vein system, Black Peak area, Copper Hill, Globe Hills, Globe Hills District, Globe-Miami District, Gila Co., Arizona, USA

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Latitude & Longitude (WGS84): 33° 25' 36'' North , 110° 46' 4'' West
Latitude & Longitude (decimal): 33.42667,-110.76778
Other regions containing this locality:Sonoran Desert, North America

A former underground Cu-Ag-U-Au mine located in the NE¼SW¼ sec. 15, T1N, R15E, on both the Great Eastern and Iron Cap veins, about ½ mile S of Copper Hill ghost town site and about 0.7 miles SSW of Black Peak, on private land. The property consists of the Iron Cap and Bird groups of claims. The location given is for the Iron Cap shaft; the Williams shaft is about 2000 Feet NE of the Iron Cap shaft. The Iron Cap Mining Co. was organized to prospect a group of 7 claims, most of them fractional, that lie between the Copper Hill and Eureka properties of the Arizona Commercial Mining Co. The property was taken over by the National Mining Exploration Co. in November, 1905. Worked ceased in September, 1910, upon financial failure of the mine's mortgage holder. The Iron Cap Copper Co. was incorporated and the mine was reopened in July, 1912. The Bird group of claims, which adjoins the original group on the north, was acquired in 1915. Inactive from February 1921 to February 1922. Closed 1927 after lengthly litigation. Closed early in 1921 and reopened a year later. Previous owners/operators include the Iron Cap Mining Co.; National Mining Exploration Co. (1906); the Iron Cap Copper Co. (1910's and 1920's); Mr. Ralph Henderson; Louis Racine and Shapan (1958); Howard Gentry; H.P. McIntosh; and Carl Tenny (1959); and, Mr. Chas. Ireland. Owned by Mr. Howard Gentry and Mr. Carl Tenny (1959). Operated by Mr. Dale Fiscus (1963).

Mineralization is a deposit which is part of the Old Dominion vein system. It is hosted in Quartzite, schiost and limestone. An associated rock unit is diabase. The ore zone is 7.62 meters thick, strikes NE and dips 40NW. The mineralization is probably associated with an Early Tertiary, post-diabase faulting and intrusion period. Although the only outcrop of Early Tertiary Schultze Granite is at the Old Dominion Mine to the SW.

Within the bounds of the Iron Cap property, the Old Dominion vein is commonly called the Iron Cap vein. Its apex is its intersection with the low angle, northward-dipping Black Hawk fault (Black Hawk vein)Both veins, where cut by the Williams shaft, were oxidized and leached, and no ore was found.

A body of good chalcocite ore was found in the Iron Cap vein on the 800 level. It was followed southwestward to the property line and northeastward 1,200 feet to a point at which the vein fault was interrupted by a zone of cross faults known as No. 1 fault. East of the shaft a body of primary ore has been mined below the chalcocite zone to the 1,400 level. The stoped lenght ranges from 300 feet on the 1400 level, to 1,100 feet on the 1100 level.

Along the most productive part of the vein between the 700 and 1100 levels, the wall rocks are of Dripping Spring quartzite and Pioneer formation. Below the 1100 level along the primary oreshoot, the hanging wall is mostly of diabase; but near the shaft, the footwall is Pinal schist on the 1200, 1300, and 1400 levels.

One shaft, probably the Williams, was sunk to 130 feet. Later, the National Mining Exploation Co. drove it to the 802 level. A crosscut on the 350 level reached the Great Eastern vein in 1908, and by June 1910, the Iron Cap vein had been cut on the 667 level. The Iron Cap shaft was sunk to 600 feet. It is located on the south side of Copper Gulch 1,000 feet east of the Budget fault and 2,500 feet SW of the Williams shaft. Circa 1912 both shafts were deepened. The Iron Cap shaft went to the 1550 level. On the 450 level, a crosscut driven N.20ºW. intersected the Iron Cap vein 200 feet from the shaft and the Black Hawk vein 600 feet from the shaft.

After the acquisition of the Bird property, the north crosscut from the Iron Cap shaft to the Iron Cap vein on the 800 level was extended in an effort to intersect and explore the Bird vein. It was driven N36W, near the base of the Dripping Spring quartzite. At 920 feet from the shaft, it intersected the Black hawk fault, and entered diabase. At 2,130 feet from the shaft, the crosscut intersected a strong fault zone striking about N5W that may possibly be the Budget fault, but, if so, the fault is practically vertical. Near this fault zone, the crosscut was turned to bear about N.13ºE. and continued in this direction for 600 feet. A mineralized fault zone was found about 2,430 feet from the shaft, but detailed descriptions of it are lacking. The company's annual report for 1920 states that the close of the year the crosscut reached the Bird vein and passed through 5 feet of vein matter, 14 inches (40 cm) of which was highly mineralized. The vein matter was oxidized.

Workings totalled 1524 meters in length and 457 meters in depth. The Iron Cap shaft was 1500 feet deep with levels at 800, 920, 1020, 1120, 1220, 1320, 1420, and 1500 feet. The Williams shaft was 1200 feet deep with levels at 660, 765, 868, 968, and 1068 feet. The shafts connected at the 1000 foot level by 3800 feet of drift. Production from 1912 to 1927 was about 60,000,000 pounds of Cu, 4,475 oz. Au, and 1,256,500 oz. Ag, from 683,000 tons of ore. The mine is rumored to have shipped uranium ore to the Curies in France around 1912.

Mineral List

Mineral list contains entries from the region specified including sub-localities

7 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

1000 - 1200 Ma
Middle Proterozoic diabase

Age: Stenian (1000 - 1200 Ma)

Description: Dark gray to black sills (intrusions mostly parallel to bedding) in strata of the Apache Group and irregular to sheet-like intrusions in other rocks. Present in east-central and southeastern Arizona. Some sills are more than 100 m thick. Exposures are extensive north of Globe. (1050-1150 Ma)

Comments: ~ 1.1 Ga. Associated with Grand Canyon Supergroup, and Apache Group (unit Ys)

Lithology: Major:{hypabyssal basalt,gabbro}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

Localities in this Region

  • Arizona
    • Gila Co.
      • Globe-Miami District

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Arizona Mining Journal (1919), November, 1919: 42.

Schwartz, G.M. (1921), Notes on textures and relationships in the Globe copper ores, Economic Geology: 16: 322-329.

Arizona Mining Journal (1922), May 1, 1922: 24-25.

Neale, W.G., The Mines Handbook, Vol. XVII (1926): 285-287.

Schwartz, G.M. (1934), Paragenesis of the oxidized ores of copper, Economic Geology: 29: 55-75.

Peterson, N.P. (1947), Phosphate minerals in the Copper Dome copper deposit, Arizona, American Mineralogist: 32: 574-582.

Peterson, N.P. (1962), Geology and ore deposits of the Globe-Miami District, Arizona, USGS PP 342: 106-110.

Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.: 196, 407.

U.S. Bureau of Mines - Arizona Bureau of Geology and Mining Technology file data.

Arizona Department of Mineral Resources Iron Cap Mine file.

MRDS database Dep. ID #10046318, MRDS ID #M241224; and Dep. ID #10161343, MAS ID #0040070427.

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