Image from CS 13812C- Cody Shale, color, 347 Kb

Image from J0-F-52.1- Sample from the Frontier Fm. (Oil Mtn., E. Wyoming) color, 699Kb
I'd bet that the blue-grey grain with the black cement rim in the left center part of the image is a feldspar with authigenic feldspar cement

Image from J0-F-52.1- Sample from the Frontier Fm. (Oil Mtn., E. Wyoming) gray-scale, 264Kb

more sandstone images

images by Robert M. Reed Research Scientist Associate III Bureau of Economic Geology The University of Texas at Austin