"An analytical method developed by the Bureau of Mines to determine dawsonite, nahcolite, and nondawsonite alumina (called excess alumina ) extractable from Green River Formation oil shales is presented. The method requires water extraction of nahcolite followed by HC1-extraction of dawsonite and an unidentified mineral yielding excess alumina from the water-leached residue. Instrumental determination of sodium in the water extract and sodium and aluminum in the HC1 extract measures the sample's content of the minerals . Detailed evaluation shows the method to be adequately specific, precise, and reproducible and free from uncorrectab1e interferences . The method 's results define precisely the production of sodium carbonates and alumina possible from a sample of oil shale and the interval it represents. Shale -oil yields, nahcolite contents, and yields of extractable alumina determined on 83 samples representing an 821 - foot section of dawsonite-nahco1ite-bearing shale from. Colorado Corehole No . 3, drilled in the north part of Colorado's Piceance Creek Basin, are presented. These samples resulted in nahcolite contents to 53 .3 percent, oil yields to 48 .3 gallons per ton, and alumina yields to 5 . 80 percent. Use of these data to evaluate the production potential of a section of the formation are suggested."