Photomicrograph showing detail of the varves in the rich oil shale specimen in Bradley photo 321; the organic laminae indicated by marks are themselves finely laminated.

Photomicrograph showing detail of the varves in the rich oil shale specimen in Bradley photo 321; the organic laminae indicated by marks are themselves finely laminated. The mineral laminae contain considerable organic matter, but they are readily distinguished by their coarser grain and greater thickness. Enlarged 320 diameters. Garfield County, Colorado. 1927. Plate14-A in U.S. Geological Survey. Professional paper 158. 1930.

Categories: Image; Tags: Colorado Professional Paper 158, Photomicrographs, Professional Papers, Specimens, photo print

Photomicrograph of a part of the organic marlstone shown in Bradley photo 325, illustrating the regular spacing of the dark laminae; the thin section was cut abnormally thick so as to bring out the fore feebly colored organic layers. Garfield County, Colorado. 1927.

Photomicrograph of a part of the organic marlstone shown in Bradley photo 325, illustrating the regular spacing of the dark laminae; the thin section was cut abnormally thick so as to bring out the fore feebly colored organic layers. Enlarged 18 diameters. Garfield County, Colorado. 1927. Plate 12-B in U.S. Geological Survey. Professional paper 158. 1930.

Categories: Image; Tags: Bradley, W.H. Collection, Colorado Professional Paper 158, Photographers, Photomicrographs, Professional Papers, All tags... photo print, Fewer tags

Photomicrograph of a specimen from an analcite crystal bed with a distinctly tuffaceous matrix; showing sub parallel orientation of the large biotite flakes, some of which are deeply embedded in the analcite crystals. Rio Blanco County, Colorado. 1927.

Photomicrograph of a specimen from an analcite crystal bed with a distinctly tuffaceous matrix; showing sub parallel orientation of the large biotite flakes, some of which are deeply embedded in the analcite crystals. The medium toned gray matrix is chalcedony. From a bed in the north wall of White River canyon, T. 1 N., R. 103 W., enlarged 80 diameters. Rio Blanco County, Colorado. 1927. Plate 2-A in U.S. Geological Survey. Professional paper 158. 1930.

Categories: Image; Tags: Bradley, W.H. Collection, Colorado Professional Paper 158, Photographers, Photomicrographs, Professional Papers, All tags... Specimens, photo print, Fewer tags

Photomicrograph of a thin section cut parallel to the bedding of a rich stratum of oil shale studded with analcite crystals. Garfield County, Colorado. 1924.

Photomicrograph of a thin section cut parallel to the bedding of a rich stratum of oil shale studded with analcite crystals. The finest white specks are grains of dolomite and calcite; the jet-black is pyrite, which in places encircles analcite crystals; and the gray groundmass (almost obscured by the abundance of minute carbonate grains) is structure less organic matter; enlarged 36 diameters. Garfield County, Colorado. July 25, 1924. Plate 2-B in U.S. Geological Survey. Professional paper 158. 1930.

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Photomicrograph of a rich oil shale showing groups of varves distorted by small concretionary lenses of carbonate grains; enlarged 54 diameters. Garfield County, Colorado. 1927.

Photomicrograph of a rich oil shale showing groups of varves distorted by small concretionary lenses of carbonate grains; enlarged 54 diameters. Garfield County, Colorado. 1927. Plate13-B in U.S. Geological Survey. Professional paper 158. 1930.

Categories: Image; Tags: Colorado Professional Paper 158, Photomicrographs, Professional Papers, photo print

Photomicrograph showing varves in a very rich oil shale, the black parts are organic matter and the light gray areas are mineral grains; enlarged 54 diameters. Garfield County, Colorado. 1927.

Photomicrograph showing varves in a very rich oil shale, the black parts are organic matter and the light gray areas are mineral grains; enlarged 54 diameters. From the Mahogany Ledge near the head of Clear Creek in sec. 9, T. 5 S.,R. 98W. Garfield County, Colorado. 1927. Plate13-A in U.S. Geological Survey. Professional paper 158. 1930. Plate14-B in U.S. Geological Survey. Professional paper 168. 1931.

Categories: Image; Tags: Colorado Professional Paper 158, Photomicrographs, Professional Papers, photo print

Photomicrograph of a fine grained limy sandstone showing thick varves; the light bands are sandy and unusually thick, the dark bands consist largely of organic matter. Garfield County, Colorado. 1927.

Photomicrograph of a fine grained limy sandstone showing thick varves; the light bands are sandy and unusually thick, the dark bands consist largely of organic matter. Enlarged 37 diameters. Specimen from a bed in the upper part of the Green River formation at the junction of Parachute Creek and East Middle Fork of Parachute Creek in sec. 18, T. 5 S., R. 95 W., Garfield County, Colorado. 1927 Plate 12-A in U.S. Geological Survey. Professional paper 158. 1930.

Categories: Image; Tags: Bradley, W.H. Collection, Colorado Professional Paper 158, Formations, Photographers, Photomicrographs, All tags... Professional Papers, Specimens, photo print, Fewer tags

Photomicrograph of a group of euhedral sanidine and orthoclase crystals isolated from oil shale. Garfield County, Colorado. 1927.

Photomicrograph of a group of euhedral sanidine and orthoclase crystals isolated from oil shale. The grains are immersed in oil, which has a refractive index of 1.58; enlarged 80 diameters, from a bed in the western part of T. 6S, R. 95 W. Garfield County, Colorado. 1927. Plate 3-B in U.S. Geological Survey. Professional paper 158. 1930.

Categories: Image; Tags: Bradley, W.H. Collection, Colorado Professional Paper 158, Photomicrographs, Professional Papers, photo print