Tomichi Dome is a prominent igneous mountain in southeastern Gunnison County, Colorado, rising from older sedimentary ground in a setting that makes its geology especially distinctive. Formed during the Tertiary, it consists mainly of rhyolite, along with microgranite, breccia, and tuff, while the surrounding lowlands are underlain by much older Mancos Shale. Its origin has been interpreted either as a shallow laccolith formed by magma intruding into the shale or as an extrusive volcanic feature built from breccia, tuff, and later topaz rhyolite. It may be part of a broader igneous chain associated with the Rio Grande Rift and had earlier names such as Tumitche Dome before Tomichi Dome was in use by 1907.