![]() ĭunes made of small crystals of gypsum, White Sands National Park Orbital pictures from the Mars Reconnaissance Orbiter (MRO) have indicated the existence of gypsum dunes in the northern polar region of Mars, which were later confirmed at ground level by the Mars Exploration Rover (MER) Opportunity. This can lead to accumulation of elemental sulfur in oil-bearing formations, such as salt domes, where it can be mined using the Frasch process Electric power stations burning coal with flue gas desulfurization produce large quantities of gypsum as a byproduct from the scrubbers. Under reducing conditions, the sulfates it contains can be reduced back to sulfide by sulfate-reducing bacteria. Its presence indicates oxidizing conditions. Gypsum is also formed as a by-product of sulfide oxidation, amongst others by pyrite oxidation, when the sulfuric acid generated reacts with calcium carbonate. Ĭommercial 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. However, the unique conditions of the White Sands National Park in the US state of New Mexico have created a 710 km 2 (270 sq mi) expanse of white gypsum sand, enough to supply the US construction industry with drywall for 1,000 years. Pure gypsum is white, but other substances found as impurities may give a wide range of colors to local deposits.īecause gypsum dissolves over time in water, gypsum is rarely found in the form of sand. Gypsum is the most common sulfate mineral. It is often associated with the minerals halite and sulfur. Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures. Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. Deposits are known to occur in strata from as far back as the Archaean eon. Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks. It also forms some of the largest crystals found in nature, up to 12 m (39 ft) long, in the form of selenite. In arid areas, gypsum can occur in a flower-like form, typically opaque, with embedded sand grains called desert rose. ![]() A very fine-grained white or lightly tinted variety of gypsum, called alabaster, is prized for ornamental work of various sorts. In hand-sized samples, it can be anywhere from transparent to opaque. ![]() Finally, it may also be granular or quite compact. Selenite may also occur in a silky, fibrous form, in which case it is commonly called "satin spar". Selenite contains no significant selenium rather, both substances were named for the ancient Greek word for the Moon. Gypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite. Elongated and generally prismatic crystalsĬonchoidal on plane). For other uses, see Gypsum (disambiguation).Ĭolorless (in transmitted light) to white often tinged other hues due to impurities may be yellow, tan, blue, pink, dark brown, reddish brown or gray
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