The U.S. Department of the Interior, Bureau of Mines, has been conducting minerals recovery research in support of the nation's geothermal program since 1974. The Bureau's program of laboratory and field studies has focused on determining the materials of construction for geothermal resource recovery plants and on the recovery of mineral values from the geobrines. An analytical program has been conducted at the Avondale Research Center to determine the chemical constituents of some high- and low-salinity geobrines found in the Imperial Valley of California. Data are reported for the early stages of brine production of four geothermal wells--the low-salinity, medium-enthalpy brines from the East Mesa Known Geothermal Resource Area (KGRA), Mesa 6-1, and 6-2, and the high-salinity, high-enthalpy brine from the Salton Sea KGRA, Magmamax 1 and Woolsey 1. The reported results indicate the importance of the operating and engineering history, the operating parameters during sampling, and the method of sampling in order to evaluate the chemical analyses.