Arkose is a coarse sandstone rich in feldspar that typically exhibits a pink, gray, or reddish hue. The substance closely resembles granite, the rock from whose disintegration it is commonly derived, in appearance and is frequently utilized as a building material. Quartz is the principal material in arkose, but feldspar composes at least 25 percent of the material, and calcite, iron oxide, and micas may be present as well. When exposed to dilute hydrochloric acid (a frequent method of quickly indicating rock types), arkose effervesces slightly.