A preliminary mineral-resource potential assessment of western Rio Arriba County involves analyses of available published and unpublished geologic, geochemical, geophysical, and economic data and a brief reconnaissance. Mineral-resourae potential is an assessment of the favorability that a corn-nodity will occur in substantial concentrations in a given area that can be exploited under current or future economic conditions. A classification of high, moderate, low, very low, or unknovn is assigned. A high mineral-resource potential exists in a n a s where geologic and economic data indicate an excellent probability that economic mineral deposits occur there. Moderate or low mineral-resource potential exists in areas where the data indicate a lesser probability that economic mineral deposits occur. A classification of very low potential is reserverl for areas where sufficient information indicates that an area is unfavorable for economic deposits. A classification of uxknown mineral-resource potential is assigned to areas where eitller necessary geologic, geochemical, geophysical, and economic data are inadequate to otherwise classify an area or where any other classification (high, moderate, low, or very low) would bs..misleading. Some areas have not been evaluated for specific commodities because of lack of useable data.Oil and gas are currently being produced in western Rio Arriba County and the resource potential is high in Cretaceous, Jurassic, and upper Paleozoic rocks. Clay in the Mesa Prieta area has a moderate resource potential. There is a high resource ii potential for crushed and dimension stone throughout the entire area. Limestone resource potential is high in the Todi1t"J Limestone in southeastern Rio Arriba County. A moderate resource potential exists for copper and silver in the Chinle Formation in the Nacimiento Mountains, deep coal i the Menefee and Fruitland Formations in the San Juan Basin, C02 and helium in the San Juan Basin, and limestone in the Madera Formation. An unknown resource potential exists for silica sand, zeolites, and barite. Additional geologic mapping and geochemcial studies are required in areas with active claims, areas of aggregate resources, and along the Kirtland-Fruitland contact for barium resource potential. Isopach facies and structure-contour maps and additional petroleum tests are suggested to enhance evaluation of the petroleum resources. Detailed studies of the mineralogy and chemistry of clay deposits are required to fully assess their potential.