Small quantities of autunite and gummite (?) occur in tuffaceous sedimentary rocks of the Rosamond formation of Miocene age at the Rosamond prospect. The property is about 10 miles south of Mojave, Jern County, California, in the western Mojave Desert. Examination of the propert in January 1952, by George W. Walker and Luther H. Baumgardner of the U.S. Geological Survey, indicates the the autunite occurs principally as coating on fracture and joint surfaces and, to a less extent, as disseminations in the tuffaceous rocks adjacent to faults. A waxy, reddish-brown, radioactive mineral, here called gummite (?), is found in small quantities on slickensided fault surfaces associated with iron oxides and chlorite (?). The uranium minerals are erratically distributed over an area of about 15 acres. Assay of 12 samples indicate a uranium content ranging from 0.002 to 0.59 percent and an average content of slightly less than 0.08 percent uranium.