Mineral production is essential to our civilization because minerals provide the raw materials which allow our society to function. Pima County is endowed with many mineral resources, not only copper mines, but also the important products such as sand, gravel, and limestone used everyday in supporting the infrastructure of our cities. It is essential that these mineral resources, and the lands where they occur, remain available for exploration and development. Mining is a significant part of Pima County’s economy. Last year, copper producers bought $186 million worth of goods and services from Pima County firms. Local governments in the Tucson Metropolitan area received $10 million in direct tax payments. Residents received over $88 million in personal income directly from the copper industry. When revenue from other mining operations and the economic multiplier effect of expenditures is taken into account, the real value of mining is nearly five times greater than these numbers. This report presents an assessment of the mineral resources of Pima County based on hard data derived from many experienced geologists working in the private sector and from publications of state and federal government agencies. Pima County has a unique, and complex, geological history which makes it critical habitat for large copper deposits, geothermal resources, and many industrial minerals such as sand, gravel, gypsum, and limestone. This report documents known occurrences of these mineral deposits, and delineates areas with the greatest potential for future discovery of additional mineral deposits, based on existing geological and geochemical data, and upon proven methods of investigation. Most areas favorable for mineral deposits coincide with portions of the Sonoran Desert Conservation Plan’s proposed biological reserves. We should note that mineral exploration and production is not necessarily incompatible with conservation. The Sonoran Desert Conservation Plan addresses six elements: ranching, historical and cultural preservation, mountain parks, riparian protection, critical and sensitive habitats, and biological corridors. An important seventh element is missing: mineral resources. This report outlines seven areas which are critical habitats for undiscovered mineral deposits, areas which need to be as carefully protected and defined as are habitats for endangered species. If these prospectable areas are withdrawn from exploration and development, the availability of our future sand and gravel, porphyry copper deposits, and other mineral deposits will become endangered and, in a real sense, the availability of vital minerals will eventually become extinct in Pima County. The impact of such a development on Pima County and the Tucson Metropolitan area will be considerable. If the sand and gravel deposits can no longer operate within a reasonable distance of construction sites, the costs of new construction and of renovations of existing infrastructure will greatly increase. Although the direct impact of curtailing copper exploration and development will not be immediately noticeable to most citizens of Pima County, the longer term impact could affect the cost and availability of many common products we use today, and also could be detrimental to the future national security of the United States. Members of the Southwestern Minerals Exploration Association strongly recommend that the potential mineral bearing areas be kept available for future development, and urge the planners of the Sonoran Desert Conservation Plan to consider minerals as a critical Seventh Element in the planning process - an element that needs protection as much as many of the “vulnerable” species being considered.