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Questa Molybdenum Mine (Questa Mine; Moly Mine; R and S Mine), Questa, Taos Co., New Mexico, USA

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Latitude & Longitude (WGS84): 36° 42' 15'' North , 105° 30' 23'' West
Latitude & Longitude (decimal): 36.70417,-105.50639
Köppen climate type:Dfb : Warm-summer humid continental climate

A molybdenum-rhenium mine owned by Molycorp, a subsidiary of Unocal Corp. Produced 4,760 tons of Mo in concentrates (1984). In 2011, the mine was declared a superfund site - on June 2, 2014 the mine was declared permanently closed.

Located nine miles from Questa, the mine opened in 1916 as the R&S Molybdenum mine. It was purchased by Molycorp Minerals in 1950 and became a subsidiary of Chevron in 2005. Formerly an open pit excavation, the Chevron Questa mine had operated as an underground mine since 1982.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

26 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

Pliocene - Eocene
2.588 - 56 Ma

ID: 2860935
Tertiary intrusive rocks of intermediate to silicic composition

Age: Cenozoic (2.588 - 56 Ma)

Description: Includes monzonitic to granitic plutons, stocks, laccoliths, and porphyritic dikes in deeply eroded magmatic centers; and andesitic, dacitic, or rhyolitic plugs and dikes near cauldrons or stratovolcanoes. In the Latir field, fine-grained rhyolitic dikes commonly cut coarse-grained granitic plutons. Includes alkaline laccoliths, plugs, and dikes in Colfax County. North-trending dikes near Capitan include some mafic diabase dikes.

Lithology: Major:{granitic,syenitic}, Minor:{felsic hypabyssal,mafic hypabyssal}

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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Schilling, J. H. (1956) Geology of the Questa Molybdenum Mine Area, Taos County, New Mexico. New Mexico Bureau of Geology and Mineral Resources Bulletin 51.
Clark, K. F. and C. B. Read (1972), Geology and Ore Deposits of Eagle Nest area, New Mexico. New Mexico Bureau of Geology and Mineral Resources Bulletin 94.
Mining Annual Review (1985): 118 & 331.
Cline, Jean S. & Bodnar, Robert J. (1994): Direct evolution of brine from a crystallizing silicic melt at the Questa, New Mexico, molybdenum deposit. Economic Geology 89, 1780-1802.
Northrop, S.A. and LaBruzza, F.A. (1996), Minerals of New Mexico, revised Third Edition.
Campbell, A.R., and Lueth, V.W. (2008): Isotopic and textural discrimination between hypogene, ancient supergene, and modern sulfates at the Questa Mine, New Mexico. Applied Geochemistry 23, 308-319.
Junxing Zhao, Kezhang Qin, Guangming Li, and Jinxiang Li (2011): Characteristics of alteration and mineralization in the Sharang porphyry molybdenum deposit in the northern margin of Gangdese and comparison with typical porphyry molybdenum deposits in the world. Geology and Exploration 47(1), 54-70.
DeMark, Ramon S. (2015): Minerals of the Questa Moly Mine, Taos County, New Mexico. 36th Annual New Mexico Mineral Symposium Program & Abstracts, page 9.

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