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Peridot Mesa (Peridot occurrence 38), San Carlos, San Carlos Indian Reservation, Gila Co., Arizona, USA

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Latitude & Longitude (WGS84): 33° 19' 49'' North , 110° 29' 35'' West
Latitude & Longitude (decimal): 33.33028,-110.49306
Other regions containing this locality:Sonoran Desert, North America
Köppen climate type:BSk : Cold semi-arid (steppe) climate

A peridot/olivine mine located in secs. 18, 19 & 30, T1S, R19E; and in secs. 22-27, T1S, R18E, immediately SW of San Carlos. This site has been described as the most productive peridot locality in North America.

Mineralization is a mesa capped by a basalt flow from 10 to more than 100 feet thick, underlain by flat-lying tuffs, siltstones & gravels. These sedimentary rocks are regarded as the equivalent of the Gila Conglomerate and therefore of Pliocene or Pleistocene age. The peridot occurs in roughly ellipsoidal bombs, or segregations, in basalt & cinders erupted from a volcanic cone that occupies the SW corner of the mesa. It is present as euhedral crystals and as rounded grains. The ellipsoidal segregations containing the peridot make up 25 to 40% of the rock volume and average 3 to 8 inches in maximum diameter.

Workings: Mined intermittently by individuals (up to 50), who worked scattered portions of the deposit using hand methods. Also was mined by 5-10 person operations that are more mechanized. Most stones are gathered from debris resulting from the erosion of basalt. Prime locations are around the rim of the volcanic cone, in washes adjacent to the cone, and in small canyons that breach the north rim of the mesa.

Assay data: The olivine zone should maintain a minimum olivine content of 30% to be economical. The portions of the deposit olivine-rich zone with greater than 30% olivine are: SE¼ sec. 15, S½ sec. 14, sec. 22, N½ and SW¼ sec. 23, NW¼ sec. 26, and the NE¼ sec. 27, T1S, R18E.

Mineral List

6 valid minerals.

Rock Types Recorded

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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

Holocene - Zanclean
0 - 5.333 Ma

ID: 2842290
Holocene to middle Pliocene basaltic rocks

Age: Cenozoic (0 - 5.333 Ma)

Description: Mostly dark-colored basaltic lava and cinders young enough that some original volcanic landforms are still apparent. Includes a small amount of andesite, dacite, and rhyolite. Rocks of this map unit are largely restricted to six areas widely distributed in Arizona: San Francisco and Uinkaret volcanic fields in northern Arizona (0-4 Ma); Springerville (0-4 Ma) and San Carlos (0-2 Ma) volcanic fields in east-central Arizona; and San Bernardino (0-1 Ma) and Sentinel (1-4 Ma) volcanic fields in southern Arizona. Rocks of this unit are also present in the extreme southwestern part of Arizona where they were erupted at the edge of the Pinacate volcanic field (0-2 Ma) in northwestern Sonora. (0-4 Ma)

Comments: Largely in six volcanic fields: San Francisco, Unikaret, Springerville, San Carlos, San Bernardino, and Sentinal.

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

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

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.


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Bromfield, C.S. & Shride (1956), Mineral resources of the San Carlos Indian Reservation, AZ, USGS Bull. 1027-N: 686-687.
Peirce, H.W. (1969), Gem Materials, in USGS & Arizona Bureau of Mines & US Bureau of Reclamation, Mineral and Water Resources of Arizona, Arizona Bureau of Mines Bull. 180 (USGS Bull.871): 359.
Rabb, D.D. and Vuich, J.S. (1975) San Carlos Indian Reservation Peridot Mine: Inspection Report B75-2, Arizona Bureau of Mines, University of Arizona, Tucson, 34 pp.
Moore, R.T. and Vuich, J.S. (1977) An Evaluation of the Olivine Resources of the San Carlos Apache Indian Reservations and Recommendations for Potential Development. NADSAT Project Completion Report No. 1. Arizona Bureau of Mines, 34 pp.
Garcia, M.O., et al (1980), Volatiles in Ti-rich amphibole megacrysts, southwestern USA, American Mineralogist: 65: 306-312.
Koivula, John (1981), San Carlos peridot, Gems and Gemology: 17: 4: 205-214
Peirce, H. Wesley (1990), Arizona Geological Survey Industrial Minerals card file.
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd. ed.: 114.
MRDS database Dep. ID #10060353, MRDS ID #TC10730; and Dep. ID #10113001, MAS ID #0040070542.
Uchida et. al (2005) Single Crystal x-ray diffraction of spinels from the San Carlos Volcanic Field: Spinel as a geothermometer: American Mineralogist v. 90 p. 1900-1908.
Hadnott B.A., Ehlmann B.L. and Jolliff B.L. (2017) Mineralogy and chemistry of San Carlos high-alkali basalts: Analyses of alteration with application for Mars exploration: American Mineralogist 102, 284-301. (individual microprobe analyses of all phases in the basalt plus a photo of the outcrop.)

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