Pegmatite occurs widely in Nevada and northwestern Arizona, but little mining has been done for such pegmatite minerals as mica, feldspar, beryl, and lepidolite. Reconnaissance for beryl-bearing pegmatite in Nevada and in part of Mohave County, Arizona, and detailed studies in the Dawley Canyon area, Elko County, Nevada, have shown that beryl occurs in at least 11 districts in the region. Muscovite has been prospected or mined in the Ruby and Virgin Mountains, Nevada, and in the Mohave County, Arizona. Feldspar has been mined in the southern part of the region near Kingman, Arizona, and in Clark County, Nevada. The pegmatites in the region range in age from Precambrian to late Mesozoic or Tertiary. Among the pegmatite minerals found or reported in the districts studied are beryl, chrysoberyl, scheelite, wolframite, garnet, tourmaline, fluorite, apatite, sphene, allanite, samarskite, euxenite, gadolinite, monazite, autunite, columbite-tantalite, lepidolite, molybdenite, and pyrite and other sulfide minerals. The principal beryl-bearing pegmatites examined are in the Oreana and Lakeview (Humboldt Canyon) areas, Pershing County; the Dawley Canyon area in the Ruby Mountains, Elko County, Nevada; and on the Hummingbird claims in the Virgin Mountains, Mohave County, Arizona. Beryl has also been reported in the Marietta district, Mineral County; the Sylvania district, Esmeralda County; near Crescent Peak and near Searchlight, Clark County, Nevada; and in the Painted Desert near Hoover Dam, Mohave County, Arizona. Pegmatites are abundant in the Ruby Mountains, chiefly N. of the granite stock at Harrison Pass. In the Dawley Canyon area of 2.6 sq. mi. at least 350 pegmatite dikes more than 1 ft. thick were mapped, and beryl was found in small quantities in at least 100 of these dikes. Four of these dikes exceed 20 ft. in thickness, and one is 55 ft. thick. A few pegmatites were also examined in the Corral Creek, Gilbert Canyon, and Hankins Canyon areas in the Ruby Mountains.