From Sandstone to Sand Paintings Well-rounded grains of nearly pure quartz sand compose the St. Peter Sandstone. This formation is up to 200 ft thick in the Pikes Peak region, and its massive beds stand out among the bluffs and steep-walled ravines. Of special interest in its lower portion are dramatic reddish-orange swirls and bands of iron-oxide cements. These colors were imparted by mineralized groundwater moving through the porous sandstone.    Photo by Ray Anderson.   Captivated by the array of colors at Pictured Rocks or Sand Cave, as the site is known, Andrew Clemens, an 1880s resident of McGregor, created exquisite, three-dimensional sand paintings in bottles. During his 20s and 30s, he created intricate designs and pictures by layering loose sand into drug jars, color by color, upside down through their narrow openings. Completed artworks were sealed with wax and inverted. Shown left are two sides of one jar, with George Washington astride a white horse on one side, and two Native Americans, the State Seal of Iowa (including motto), and a steamboat on the other. Note Clemens’ signature in the red sand below the boat.         Photo courtesy of State Historical Society of Iowa – Des Moines.  Photographer: Chuck Greiner.     Source for Andrew Clemens information: Wagasky, Rashelle, 1997. One in a Million. Iowa Heritage Illustrated, State Historical Society of Iowa, Spring, 1997, p. 48-49.  Source for geological information: Anderson, R.R. and Bunker, B.J. (eds). 2000. The Natural History of Pikes Peak State Park, Clayton County, Iowa. Geological Society of Iowa, Guidebook 70, Nov. 2000, 139 p.    Adapted from Iowa Geology 2001, No. 26,  Iowa Department of Natural Resources