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Photomicrograph of a group of minute apophylite crystals isolated from oil shale. Garfield County, Colorado. 1927. Photomicrograph of a group of minute apophylite crystals isolated from oil shale, showing nearly perfect prismatic crystals and also irregular forms. From a thin rich layer of oil shale in the "Mahogany ledge" at the U.S. Bureau of Mines experimental min in sec. 23, T. 6 S., R. 96 W. The grains are immersed in an oil which has a refractive index of 1.58; enlarged 500 diameters. Garfield County, Colorado. 1927. Plate 3-A in U.S. Geological Survey. Professional paper 158. 1930. Categories: Image; Tags: Bradley, W.H. Collection, Garfield County, Colorado, Mills, Mines, Quarries, Photographers, photo print Algae reef from the "Manti Beds" at Manti. San Pete County, Utah. 1925. Algae reef from the "Manti Beds" at Manti, the dark areas are partly silicified and contain the filamentous algae shown in plate 33 (see bwh00233, 234, or 235), natural size. San Pete County, Utah. 1925. Categories: Image; Tags: Bradley, W.H. Collection, Mills, Mines, Quarries, Photographers, San Pete County, Utah, photo print