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New Cornelia Mine (Ajo Mine), Ajo, Little Ajo Mts, Ajo District, Pima Co., Arizona, USA

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Latitude & Longitude (WGS84): 32° 21' 20'' North , 112° 51' 54'' West
Latitude & Longitude (decimal): 32.35556,-112.86500
GeoHash:G#: 9mz8pdnhy
Other regions containing this locality:Sonoran Desert, North America
Locality type:Mine
Köppen climate type:BWh : Hot deserts climate

A former large-output surface Cu-Ag-Au-Mo-Zn-Ti-Nb-Rb-Gemstones mine located in the SE ¼ sec. 22, SW ¼ sec. 23, NW ¼ sec. 26 & the NE ¼ sec. 27, T. 12S., R.6W., about ½ mile (0.8 km) South of Ajo. Discovered by the Spaniards in 1750. First produced in modern times in 1917. Owned at times, or in part, by the Arizona Copper Mining & Trading Co.; St. Louis Copper Co.; the Rescue Copper Co.; Cornelia Copper Co.; New Cornelia Copper Co. (1912-1916); Calumet & Arizona Copper Co.; and the New Cornelia Division, Phelps Dodge Corp.

Mineralization is an elliptical ore body 2,011.63 meters long, 1,206.98 meters wide, 487.68 meters deep, and 304.8 meters thick, with veinlets and disseminations of chalcopyrite, bornite, and minor pyrite, oxidized in the upper part to carbonates, silicates, and minor chalcocite, deposited in fractured and faulted, altered Laramide quartz monzonite and bordering quartz diorite facies, and often in close association with irregular pegmatite zones in the intrusive. Mineralization extends into bordering intruded and altered Cretaceous volcanics. Minor spotty molybdenite and sphalerite. Ore control was the fracturing of the porphyry. Ore concentration was governed by the permeability of rocks to mineralizing fluids; some secondary copper on fractures. Alteration included sericitic, clay, chloritization, kaolinization, silicification with oxidation down to the water table. The host rock unit is the Chico Shuni (Cornelia). An associated rock unit is the Cornelia pluton.

Contact of oxidized and sulfide ore is sharp. There is no leached overburden. Gold is more closely associated with copper sulfides than with pyrite. Units present include quartz monzonite, quartz diorite, granodiorite, Equigranular quartz monzonite, porphyritic quartz monzonite, and porphyritic micro-quartz monzonite.

Local structures include NNW fracture zones and a number of major faults with large displacements.

The working is a huge open pit operation (about 3,000 feet long and nearly 2,000 feet wide) at 750 feet deep. Haulage was by internal railroad installed in the pit. Total production from 1917 through 1972 amounts to some 350,000,000 tons of ore averaging about 0.8% Cu, 0.05 oz. Ag/T and 0.004 oz. Au/T. Higher grade ore was mined in the early years and lower grade ore in more recent years.

Mineral List

85 valid minerals. 2 (TL) - type locality of 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 Macrostrat.org

Quaternary - Miocene
0 - 23.03 Ma

ID: 3185380
Cenozoic sedimentary rocks

Age: Cenozoic (0 - 23.03 Ma)

Lithology: Sedimentary rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Ypresian - Campanian
47.8 - 83.6 Ma

ID: 2847840
Early Tertiary to Late Cretaceous volcanic rocks

Age: Phanerozoic (47.8 - 83.6 Ma)

Stratigraphic Name: Williamson Canyon Volcanics

Description: Rhyolite to andesite and closely associated sedimentary and near-surface intrusive rocks; commonly dark gray to dark greenish gray or greenish brown. In the ranges west of Tucson, this unit includes thick welded ash-flow tuffs. Volcanic rocks of this unit are inferred to be derived from vents and volcanoes above magma chambers that solidified to form the granitic rocks of map unit TKg. These rocks are restricted to southeastern Arizona except for a small outcrop near Bagdad. (50-82 Ma)

Comments: Related, broadly, to unit TKg

Lithology: Major:{rhyolite,dacite,andesite}, Minor:{clastic}

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 Macrostrat.org, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on mindat.org. 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 mindat.org 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.


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Joralemon, I.B. (1914) The Ajo copper district, Arizona. Engineering and Mining Journal: 98: 663.
DeKalb (1918).
Greenway, J.C. (1920) Success after failures, the story of New Cornelia Copper Company as related informally by Col. John C. Greenway. Arizona Mining Journal, v. 3, no. 8, January 1919 [1920], p. 17.
Allen, A.W. (1922) Ajo enterprise of the New Cornelia Copper Company [two parts]. Engineering and Mining Journal-Press, [Part 1] v. 113, no. 22, p. 952-956; [Part 2] v. 113, no. 23, p. 1003-1008.
Richard (1923).
Richard (1925).
Bell, G.A. (1930) Leaching practice and costs at the New Cornelia mines of the Calumet and Arizona Mining Company, Ajo, Arizona. U.S. Bureau of Mines Information Circular I.C. 6303, 30 p.
Ingham, G.R. and Barr, A.T. (1932) Mining methods and costs at the New Cornelia Branch, Phelps Dodge Corporation, Ajo, Arizona. U.S. Bureau of Mines Information Circular I.C. 6666, 18 p.
Schwartz, G.M. (1934) Paragenesis of the oxidized ores of copper. Economic Geology: 29: 55-75.
Gilluly, J. (1937) Geology and ore deposits of the Ajo quadrangle, Arizona. Arizona Bureau of Mines Bulletin 141: 68-75, 79-81.
Gilluly, James (1938) Ajo district. in: Some Arizona ore deposits. Arizona Bureau of Mines Bulletin 145: 86-90.
Gilluly, J. (1942) Mineralization of the Ajo copper district, Arizona. American Mineralogist: 27: 222-223.
Gilluly, J. (1942) The mineralization of the Ajo copper district, Arizona. Economic Geology: 37: 297-309.
Gilluly, J. (1946) The Ajo mining district, Arizona. USGS Professional Paper 209.
Galbraith, F.W. (1947) Minerals of Arizona. Arizona Bureau of Mines Bulletin 153: 16, 17, 19.
Schwartz, G.M. (1947) Hydrothermal alteration in the 'porphyry copper' deposits, Arizona. Economic Geology: 44: 253-277.
Gilluly, James (1952) Geology of the New Cornelia mine, Ajo, Arizona (abstracted from James Gilluly, in Shride, A.F., McKee, E.D., and Harshbarger, J.W., editors, Guidebook for field trip excursions in southern Arizona.) Geological Society of America, Cordilleran Section Meeting, April 10-14, 1952, Tucson, Arizona. Arizona Geological Society, p. 58-61.
Schaller, W.T. and Vlisidis, A.C. (1958) Ajoite, a new hydrous aluminum copper silicate. American Mineralogist: 43: 1107-1111.
Schwartz, G.M. (1958) Alteration of biotite under mesothermal conditions. Economic Geology: 53: 164-177.
Galbraith, F.W. and Brennan, D.J. (1959) Minerals of Arizona: 70, 75, 111.
Hardwick, W.R. (1960) Open-pit copper mining methods at New Cornelia Branch, Phelps Dodge Corp., Pima County, Arizona. U.S. Bureau of Mines Information Circular I.C. 7938, 83 p.
Hutton, C.O. and Vlisidis, A.C. (1960) Papagoite, a new copper-bearing mineral from Ajo, Arizona. American Mineralogist: 45: 599-611.
Sun, M.S. (1961) Differential analysis of shattuckite. American Mineralogist: 46: 67-77.
Newberg, D.W. (1964) X-ray study of shattuckite. American Mineralogist: 49: 1234-1239.
Sinkankas, J. (1964) Mineralogy for Amateurs. D. Van Nostrand Co., Inc., Princeton, NJ.
Guillebert, C. and Le Bihan, M.T. (1965) Contributions à l'étude structurale des silicates de cuivre: Structure atomique de la papagoite. Bulletin de la Société française de minéralogie et de cristallographie: 88: 119-121.
Dixon, D.W. (1966) Geology of the New Cornelia Mine, Ajo, Arizona. in Titley, S.R., and Hicks, C.L., editors, Geology of the porphyry copper deposits, southwestern North America. Tucson, University of Arizona Press, p. 123-132.
Mrose, M.E. and Vlisidis, A.C. (1966) Proof of the formula of shattuckite, Cu5(SiO3)4(OH)2 (abs.). American Mineralogist: 51: 266-267.
Vlisidis, A.C. and Schaller, W.T. (1967) The formula of shattuckite. American Mineralogist: 52: 782-786.
May, B.T. (1968) Magnetic properties of rocks associated with the New Cornelia porphyry copper deposit, Pima County, Arizona. Tucson, University of Arizona, Ph.D. dissertation, 159 p.
Wadsworth, W.B. (1968) The Cornelia pluton, Ajo, Arizona. Economic Geology: 63(2): 101-115.
Keith, Stanton B. (1974) Arizona Bureau of Geology & Mineral Technology, Geological Survey Branch Bulletin 189, Index of Mining Properties in Pima County, Arizona: 83 (Table 4).
Wadsworth, W.B. (1974) Cornelia pluton, Arizona; petrogenesis inferred from grain-transition probabilities [abs.]. Eos, Transactions, American Geophysical Union: 55(4): 485.
Cox, C.J. (1975) unpublished data.
Wadsworth, W.B. (1975) Petrogenetic significance of grain-transition probabilities, Cornelia Pluton, Ajo, Arizona. in Quantitative studies in the geological sciences. Geological Society of America Memoir 142, p. 257-282.
Evans, H.T. and Mrose, M.E. (1977) The crystal chemistry of the hydrous copper silicates, shattuckite and plancheite. American Mineralogist: 62: 491-502.
Arizona Pay Dirt (1979) Phelps Dodge Announces Pit Expansion that will Carry Ajo Mine Through 1980's. August 1979: 30.
Arizona Pay Dirt (1980) Phelps Dodge is Constructing Moly Plant at Ajo. April 1980: 22.
Arizona Pay Dirt (1981) (Supplement) Ajo, in Phelps Dodge – A Copper Centennial, 1881-1981. Summer, 1981: 64-68, 70-71, 90-91, and 180-181.
World Mining (1981) 1977-1980 production: September 1981: 50.
World Mining (1982) 1981 production: September 1982: 70.
Arizona Pay Dirt (1983) Phelps Dodge Bringing Copper Mine, Mill at Ajo Back On Line. February 1983: front cover & 5A.
Thomas, W.J. and Gibbs, R.B. (1983) Famous mineral localities: The New Cornelia mine, Ajo, Arizona. Mineralogical Record: 14: 283-298.
Singer, D.A., Berger, V.I., and Moring, B.C. (2008) Porphyry copper deposits of the world: Database and grade and tonnage models, 2008. US Geological Survey Open-File Report 2008-1155.
Anthony, J.W., et al. (1995) Mineralogy of Arizona, 3rd. ed.: 103, 113, 114, 132, 137, 142, 146, 163, 166, 174, 183, 185, 190, 196, 202, 216, 220, 233, 235, 246, 272, 286, 294, 298, 312, 316, 318, 319-320, 330, 334, 341, 347, 369, 383, 399.
Arizona Bureau of Mines file data.
MRDS database Dep. ID file #10027145, MRDS ID #M002273; and, Dep. ID #10283204, MAS ID #0040190008.

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