Description | Unkpapa Sandstone in Calico Canyon, Black Hills, South Dakota. Argillaceous, very fine-grained, massive quartz wacke sandstone; moderately indurated but friable, permeable, no indication of cement. Colors range from pale yellowish orange (10YR 8/6) to grayish orange (10YR 7/4) to pale red purple (5RP 6/2) to pinkish gray (5Y 8/1). Color banding common, planar, curved, and Liesegang. |