Arizona has two major types of copper deposits: Porphyry Copper in southern and central Arizona; and the Volcanogenic Massive Sulfide Copper of the United Verde Mine in Jerome of central Arizona. A third copper source includes copper of breccia pipes of the Breccia Pipe Province of northern Arizona.

The majority of the copper mined in Arizona comes from porphyry copper deposits, which consists of copper ore deposits associated with intrusive igneous rocks similar to granite. Porphyry describes the typical texture of these rocks, in which individual mineral grains about 2mm to 125mm in size, are surrounded by smaller grains that are barely visible to the naked eye. These deposits are formed from saline, metal-bearing fluids expelled from cooling magma. Interaction of the fluid with heated groundwater yields a corrosive liquid that chemically alters rocks adjacent to the intrusion.

The intrusive activity responsible for Arizona's porphyry copper deposits occurred about 70 million years ago, in the earth's crust deep below the ground surface. The rich metal deposits were subsequently exposed millions of years later by faulting and erosion. Weathering processes, which accompany uplift and erosion, further concentrated the copper. This "secondary enrichment" occurred when pyrite (iron sulfide) oxidized, dissolved in rainwater, and formed an acidic iron sulfate solution that dissolved the main copper-ore mineral, chalcopyrite (copper-iron sulfide). The dissolved copper was redeposited, principally as the mineral chalcocite (copper sulfide). Bacteria may also play an important role in both the dissolution and redeposition of the copper.