Tomichi Dome is a roughly hemispherical mountain in Gunnison County, southwestern Colorado (Fig. 1), some thirty miles west of the Continental Divide and about 20 miles east of Gunnison. Its crest is in the northeast comer of section 28, T. 49 N., R. 4 E. The new highway from Pitkin to Salida passes through Waunita Hot Springs in section 11, and the dome can best be ascended on foot from the northern side, where the hot springs are located.
The dome is mapped on the Hayden atlas1 and on the geological map of Colorado published in 1913, as Carboniferous sediments. More recently, the fact that it consists mainly of igneous rock has been recognized, but geologists appear generally to regard this as intrusive. No detailed map of the area has hitherto been published, however, nor, so far as is known, have any careful petrographic studies of its . . .