Photo: tsaiproject, Sunset (Some rights reserved)
Wikipedia: Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard/sidewalk chalk, and drywall.
Conditions of the White Sands National Park (New Mexico) have created a 710 km2 (270 sq mi) expanse of white gypsum sand. Commercial exploitation of the area, strongly opposed by area residents, was permanently prevented in 1933 when President Herbert Hoover declared the gypsum dunes a protected national monument. In 2019 the monument became a national park.
Orbital pictures from the Mars Reconnaissance Orbiter (MRO) have indicated the existence of gypsum dunes in the northern polar region of Mars.
NASA/JPL/University of Arizona North Polar Gypsum Dunes