URGENT MESSAGE: We need $75,000 to survive. Click here to find out why.
Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for Educators
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
StatisticsThe ElementsUsersBooks & MagazinesMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

Twin Buttes Mine (Twin Buttes Open Pit Mine), Twin Buttes, Pima District (Olive District; Mineral Hill District; Twin Buttes District), Sierrita Mts, Pima Co., Arizona, USA

This page is currently not sponsored. Contact us for sponsorship opportunities.
Lock Map
Latitude & Longitude (WGS84): 31° 53' 35'' North , 111° 2' 5'' West
Latitude & Longitude (decimal): 31.89306,-111.03500
GeoHash:G#: 9t9j3mfy8
Other regions containing this locality:Sonoran Desert, North America
Owned/operated by:Freeport-McMoRan (100%)
Locality type:Mine (Active) - last checked 2018
Köppen climate type:BSk : Cold semi-arid (steppe) climate

A former large surface Cu-Ag-Mo-Zn-Pb-Au-U-Wollastonite mine located in the SW ¼ sec. 5, and the SE¼ sec. 6, T.18S., R.13E. (Twin Buttes 15 minute topo map), 25 miles S of Tucson at Twin Buttes. Previously owned by The Anaconda Co. & Anamax Mining Co. (1975-1985).

Mineralization is dissemination, fracture filling, and bunchy replacements of copper and molybdenum minerals, with minor lead and zinc, oxidized with erratic enrichment in the upper part, in a folded and faulted complex of Paleozoic limestone, silicated limestone, and impure argillaceous limestone; Cretaceous siltstone, arkose, tuffs, and quartzites, and Laramide intrusive quartz monzonite. Ore control was along contacts of dike-like quartz monzonite porphyry with sedimentary rocks. Ore concentration was the secondary enrichment of sulfides. Alteration includes a 200 foot thick ozide zone, skarn, recrystallization, biotitization, and sericitization. Host rock units include the Angelica Arkose and the Concha Limestone. The ore zone depth to top was 121.92 meters and depth to bottom was 243.84 meters.

Total sulfide content generally corresponds to total copper content. The strongest mineralization is found in silicated, garnetized, chloritized limestone & siltstone. The quartzite is only weakly mineralized. Clastics are mineralized on the S, and better Cu values occur in contact with porphyry to the SE. The porphyry shows only scattered and weak mineralization. The sulfide zone is 600-800 feet below the surface. Wollastonite occurs in skarn.

Local structures include sediments folded and contorted, dipping steeply; several fault systems, stratigraphic unconformities.

Workings are an open pit operation at 1,524 meters long, 1,219.2 meters wide and 243.84 meters deep. Planned size was 9,000 X 6,500 feet and 1,000 feet deep. Production from 1965 through 1972 amounted to some 29 million tons of ore averaging about 0.8% Cu, 0.1 oz. Ag/T, and minor Mo, Pb & Au.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.

Mineral List

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

69 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

Holocene - Gelasian
0 - 2.588 Ma

ID: 2774482
Quaternary surficial deposits, undivided

Age: Pleistocene (0 - 2.588 Ma)

Description: Unconsolidated to strongly consolidated alluvial and eolian deposits. This unit includes: coarse, poorly sorted alluvial fan and terrace deposits on middle and upper piedmonts and along large drainages; sand, silt and clay on alluvial plains and playas; and wind-blown sand deposits. (0-2 Ma)

Lithology: Major:{sand,silt,clay}

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]

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]

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

Localities in this Region
Show map

  • Arizona
    • Pima Co.
      • Sierrita Mts
        • Pima District (Olive District; Mineral Hill District; Twin Buttes District)
          • Twin Buttes
            • Twin Buttes Mine (Twin Buttes Open Pit Mine)

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.


Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Ref.: Galbraith, F.W. (1947), Minerals of Arizona, Arizona Bureau of Mines Bull. 153: 20.
Galbraith, F.W. & D.J. Brennan (1959), Minerals of Arizona: 94.
Paydirt (1970), May 27, 1970.
World Mining (1971 & 1972).
Paydirt (1972), Aug 28, 1972.
Keith, Stanton B. (1974), Arizona Bureau of Geology & Mineral Technology, Geological Survey Branch Bull. 189, Index of Mining Properties in Pima County, Arizona: 138 (Table 4).
Sutulov, Alexander (1974) Copper Porphyries, University of Utah Printing Services (mill).
Kelly, J.L. (1976) Geology of the Twin Buttes copper deposit, Pima County, Arizona [abs.]: Economic Geology: 71(3): 701.
Lorraine (1976) U.S. Bureau of Mines Information Circular 8702.
World Mining (1976): 11/76: 77.
Brooke, James N. (1977) Uranium Recovery from Copper Leaching Operations. Mining Congress Journal: 8/77: 38-41.
Hopkins, W.R. and A.J. Lynch (1977) ANAMAX Oxide Plant: A New U.S. Dimension. Engineering & Mining Journal: 2/77: 56.
Kelly, J.L. (1977) Geology of the Twin Buttes copper deposit, Pima County, Arizona: American Institute of Mining, Metallurgical, and Petroleum Engineers, Society of Mining Engineers, Transactions: 262: 110-116.
Pay Dirt (1977), (Drying concentrate, exploration): 4/25/77: 57.
Skillings Mining Review (1977) ANAMAX Mining Co.’s Copper Operations at Twin Buttes Mine (Oxide Plant, Mining Equipment, Exploration): 6/4/77: 12-16.
World Mining (1977) (Reserves, Mining Rate, Recovery, Production Stats): 5/77: 96-99.
Barter, C.F. (1978) Stratigraphy, alteration, and ore controls in the main ore zone, Twin Buttes mine, Pima County, Arizona [abs.], in Jenney, J.P., and Hauck, H.R., eds., Proceedings of the Porphyry Copper Symposium, Tucson, Ariz., March 18-20, 1976: Arizona Geological Society Digest: 11: 115-116.
Skillings Mining Review (1980): 5/24/1980: 7.
Barter, C.F., and Kelly, J.L. (1982) Geology of the Twin Buttes mineral deposit, Pima mining district, Pima County, Arizona, in Titley, S.R., ed., Advances in geology of the porphyry copper deposits, southwestern North America: Tucson, University of Arizona Press, p. 407-432.
Mining Annual Review (1985): 55.
Peirce, H. Wesley (1990), Arizona Geological Survey Industrial Minerals card file.
Mining Magazine (1991) Moly and More from Sierrita: July, 1991.
Niemuth, N.J. & K.A. Phillips (1992), Copper Oxide Resources, Arizona Department of Mines & Mineral Resources Open File Report 92-10: 13 (Table 1).
Singer, D.A., Berger, V.I., and Moring, B.C. (2005): Porphyry Copper Deposits of the World: Database, Map, and Grade and Tonnage Models. USGS Open-File Report 05-1060.
Skillings Mining Review, Vol. 59(36).
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.: 101, 111, 113, 117, 142, 146, 152, 153, 158, 163, 166, 174, 176, 196, 201, 204, 205, 207, 208, 215, 225-226, 233, 240, 246, 262, 266, 268, 272, 286, 298, 302, 305, 307, 314, 319, 324, 326, 332, 334, 341, 343, 346, 353, 354, 359, 363, 368, 377, 382, 385, 388, 391, 393, 397, 399, 400, 402, 405, 409, 411, 414, 424, 426.
Arizona Bureau of Mines file data.
MRDS database Dep. ID file #10103756, MRDS ID #M050530; and, Dep. ID #10234825, MAS ID #0040190005.

Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2018, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: June 23, 2018 18:56:41 Page generated: May 9, 2018 19:21:48
Go to top of page