Coronado Mine (Coronado Mining Co. property; Arizona Copper Co. group [in part]), Coronado vein, Copper Plate Gulch, Copper Mountain District (Clifton-Morenci District), Shannon Mts, Greenlee Co., Arizona, USA

A former surface and underground Cu-Zn-Pb-Mn mine located on 3 patented claims adjacent to the Dover Copper group, in the E½ sec. 6, T4S, R29E, on the West end of the Coronado vein, 2.0 miles west of Metcalf, on private land. Discovered in 1874 by Julius Freudenthal (Horseshoe Mine) and Morris Leszynsky (Coronado Mine). Owners included the Coronado Mining Co.; and, the Arizona Copper Co., Ltd. Produced 1913-1918. Owned and operated by the Phelps Dodge Corp., Morenci Branch. Location coordinates describe the main workings of the Coronado Mine; the Horseshoe shaft, and extension of the mine is located about 3500 feet to the west.

Mineralization is a tabular ore body 3218.6 meters long, 60.96 meters wide, with a depth to bottom of 182.88 meters, striking E-W and dipping 75S. Associated rock units are the Precambrian granite-granodiorite complex and the Coronado Quartzite. Ore control was an E-W-trending fault fissure between granite on the north and quartzite on the south. Ore concentration was surface oxidation and secondary enrichment. Secondary copper minerals (malachite and chrysocolla) occur as replacement seams in altered material along the fault. Alteration is sericitic, accompanied by quartz cementation occurring within friction breccia, diabase and crushed material of the fault. Libethenite occurs as small crystals in cavities and seams in a quartzitic gangue.

Croppings contain copper carbonates that are repalced at slight depths by chalcocite, which is in turn replaced at greater depths by pyrite and chalcopyrite. The diabase dike has a maximum width of 70 feet. Vein formation is believed to be connected with the intrusion of diabase dikes which are slightly older than the porphyry dikes throughout the district. The value of the ore depreciates rapidly with depth. The oxidized zone reaches below the 400 foot level while depth of chalcocite ore ranges from 300 to 600 feet.

Area structures include diabase and porphyry dikes connected by a fissure vein system, of which the Coronado vein is the most important. The fissure is followed in places by a diabase dike that shows evidence of crushing and movement on the vein. The Horseshoe lode consists of altered granite and contact breccia.

Tectonic component is the Coronado Granite Massif surrounded by peripheral faults. The Coronado Fault Fissure has a vertical throw of about 1200 feet.

Workings total 2865.12 meters in length and 335.28 meters in depth. Developments included the 3200 foot long Coronado incline connected to a one mile long tramway ending at the Coronado Mine (incline starts at Chase Creek). One open cut located one mile to the W of the main shafts and in Horseshoe Gulch (connected to mines by an aerial tramway); several winzes and stopes to depths of 300 feet; 200 foot deep Horseshoe shaft located to the W of the main workings; 2 other shafts, one with a depth of 1100 feet; and a 900 foot long adit. Production data prior to 1913 and after 1918 might be included in the Arizona Copper Co. Ltd. production statistics (see Longfellow Metcalf). Additional production data might be included under the Longfellow-Metcalf Mine. The Longfellow-Metcalf also includes the other Arizona Copper Co. mine data of the Detroit, Longfellow, Metcalf, Yavapai, Humboldt, Mammoth, and Joy Mines. 1905 assay values averaged 11.17 and 21.95% Cu; 67 and 48.9% Si; and, 6.91 and 9.41% Fe.

References:
Lindgren, W. & W.F. Hillebrand (1904), Minerals from the Clifton-Morenci district, Arizona, American Journal of Science: 18: 448-460.

Lindgren, W. (1905), The copper deposits of the Clifton-Morenci district, Arizona, USGS PP 43: 338-344.

Guild, F.N. (1910), The Mineralogy of Arizona, The Chemical Publishing Co., Easton, PA.

Stevens, P. (1911) The Copper Handbook: Vol. X: 356-357, Arizona Copper Co. Ltd.

Weed, W.H. (1918) The Mines Handbook, Vol. XIII: 470-471, Arizona Copper Co., Ltd.

Fairbanks, E.E. (1923), Mineragraphic notes on manganese minerals, American Mineralogist: 8: 209.

Frondel, C. & E.W. Heinrich (1942), New data on hetaerolite, hydrohetaerolite, coronadite and hollandite, American Mineralogist: 27: 48-56.

Fleischer, M. & W.E. Richmond (1943), The manganese oxide minerals: A preliminary report, Economic Geology: 38: 269-286.

Cleland, Robert G. (1952) A History of Phelps Dodge.

Watt, Roberta (1956) History of Morenci, Arizona. M.A. thesis, University of Arizona: 17.

Dunning, C.H. (1959) Rock to Riches.

Galbraith, F.W. & D.J. Brennan (1959), Minerals of Arizona: 40, 72.

Rocks & Minerals (1946): 21: 421.

Hewett, D.F. & M. Fleischer (1960), Deposits of the manganese oxides, Economic Geology: 55: 1-55.

Langton, J.M. (1973), Ore Genesis in the Morenci-Metcalf District, A.I.M.E. Transactions: 254: 256.

Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.: 188, 277.

Titley, Spencer R. (1982) Geology of the Porphyry Copper Deposits: 221-232.

Arizona Bureau of Mines Blletin 149, No. 15.

U.S. Bureau of Mines files, Coronado Mine.

USGS Clifton Quadrangle map.

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

U.S. Bureau of Land Management Mining District Sheet #840.

MRDS database Dep. ID #10109876, MRDS ID #M800425; and Dep. ID #10186633, MAS ID #0040110083.