Bedded gypsum deposits, irregularly shaped and covering about one-quarter sq mi, occur in an intrusive complex in the Absaroka Mountains. Beds lie flat and range in thickness from a few to about 15 feet. The gypsum is a grayish white to buff yellow, massive, poorly indurated rock in hand specimen, but chemical analyses show it to be 93.3 percent pure with X-ray analyses indicating only Sr and small amounts of Fe. A possible origin is deposition in a small pond or lake formed by local disruption of drainage by landslides from Crater Mountain. Pond waters may have been enriched with calcium sulfate from surface water or hydrothermal leaching of mineralized and altered zones, by upward percolating ground water or enriched hydrothermal solutions, or by primary hydrothermal solutions.