Two uranium-bearing pegmatite bodies have been discovered recently in San Bernardino County, California. Examination shows that each one contains small amounts of some uncommon minerals that are composed largely of titanium, niobium, and uranium. However, the mineral assemblages are different for each. One body, in the Cady Mountains, contains, in addition to the common feldspars and quartz, the rare minerals betafite, niobian anatase, and cyrtolite. This is the first known occurrence of betafite in California. From the Pb206/U238 ratio of betafite, the geologic age of the pegmatite has been determined as 155 million years or Middle Jurassic.
The other pegmatite body, at Pomona Tile quarry near Rock Corral, 40 miles southwest of the one in the Cady Mountains, contains euxenite and an unidentified uranium-bearing mineral, as well as the rare-earth minerals monazite and allanite and several common minerals. Euxenite is described for the first time from California. According to the lead-uranium ratio of the euxenite the age of this pegmatite is 150 million years or Middle Jurassic. The isotopic composition of lead in the euxenite has not yet been determined, so the amount of original lead is unknown.