At the western edge of the most seismically active area in North America, the range is a great uplifted plateau, cut off from the Colorado Desert to the east by the Elsinore fault system, where vertical movement over the last two million years has amounted to thousands of feet of gained elevation. As a result of metamorphosed sediments, schist, gneiss, and quartzite are abundant in the Cuyamacas, particularly in the Stonewall Mine area. Either the granodiorite comprising Stonewall Peak, or the gabbro comprising Cuyamaca Peak. As these bedrocks weather, they will eventually become the basic material of the coarse, acidic, red soil found throughout the area. Gold is a natural element that appears around granite formations because gold forms during cooling and solidification of igneous rock.
Gold commonly occurs in association with quartz, either as pure gold or as an ore.
In the Cuyamaca area, gold is associated with the metasediment called Julian schist. At mines in this area, including the Stonewall Mine in the Park, veins of gold were followed into the bedrock and the surrounding ore excavated. Most streams in the Park have small amounts of gold, since it is constantly being removed from the quartz exposures by weathering.