Gypsum is found on every continent and in a striking range of settings, from underground caves in Mexico to wind-blown dune fields in New Mexico, salt flats in Chile, ancient seabeds across Europe, and quarries that supplied the pharaohs. It is one of the most widespread evaporite minerals on Earth, forming wherever calcium- and sulfate-rich water loses enough moisture for the mineral to crystallize out. That simple recipe plays out in dozens of geological scenarios, which is why gypsum deposits span deserts, coastlines, deep basins, lake beds, and even the walls of dry caves.
Why Gypsum Shows Up in So Many Places
Gypsum is calcium sulfate bound with two molecules of water. It crystallizes when water carrying dissolved calcium and sulfate evaporates or cools past a tipping point. The most common route is straightforward evaporation of seawater or lake water in a restricted basin, but gypsum also forms when sulfide minerals like pyrite oxidize and the released sulfate meets calcium from dissolving limestone. In drained coastal soils, for instance, pyrite oxidation and carbonate weathering can drive enough calcium and sulfate into the soil solution that gypsum precipitates within months.1Soil Science Society of America Journal. Pyrite Oxidation, Carbonate Weathering, and Gypsum Formation in a Drained Potential Acid Sulfate Soil A third pathway is the hydration of anhydrite, the water-free version of calcium sulfate, which swells into gypsum when groundwater reaches it at the right temperature.
These different formation routes explain the mineral’s global spread. Anywhere an ancient sea dried up, a desert lake shrank, hot springs circulated sulfate-bearing fluids through limestone, or coastal soils oxidized buried pyrite, gypsum had an opportunity to form. And because it is soft, soluble, and easy to quarry, humans have been mining it for thousands of years.
The Mediterranean and the Messinian Salinity Crisis
Some of the thickest gypsum deposits in the world sit beneath the Mediterranean Sea floor and along its margins, relics of a dramatic episode roughly 5.3 to 6 million years ago known as the Messinian Salinity Crisis. During that period, the Mediterranean became partly or fully cut off from the Atlantic, and enormous volumes of seawater evaporated, leaving behind massive layers of salt and gypsum. The final roughly 200,000 years of that crisis produced rhythmic couplets of gypsum and marl in basins more than a thousand meters deep, each couplet tracking shifts in Earth’s orbital cycles that alternately flooded and starved the basin of Atlantic inflow.2Earth and Planetary Science Letters. High-amplitude water-level fluctuations at the end of the Mediterranean Messinian Salinity Crisis: Implications for gypsum formation, connectivity and global climate During gypsum-forming intervals, Atlantic water made up no more than about a fifth of the Mediterranean water mass; the rest came from rivers and the ancient Paratethys (precursor to the Black Sea). That mix supplied just enough sulfate and calcium for massive gypsum precipitation without diluting the basin back to normal marine salinity.
Messinian gypsum crops out today across southern Spain, Sicily, Crete, Cyprus, and parts of North Africa. The deposits are sometimes hundreds of meters thick and are quarried commercially in Italy and elsewhere. They are also a magnet for geologists studying extreme climate events, because the chemistry locked inside the gypsum crystals records water sources and temperatures from millions of years ago.
Northern Europe and the Zechstein Basin
A second giant evaporite province stretches across northern Europe. The Zechstein Basin formed during the Permian period, roughly 250 to 260 million years ago, when a shallow inland sea repeatedly evaporated across what is now the UK, the Netherlands, Germany, and Poland. Recent work on the Zechstein’s main anhydrite unit has revealed that zones of gypsum-rich buildup form a network extending over 1,000 kilometers from Britain through Germany and into Poland.3Global and Planetary Change. Major heterogeneity in evaporitic depositional systems: The genesis of kilometre-scale gypsum networks in the Zechstein Basin These buildups were originally noticed in German mines during the twentieth century, but basin-scale mapping has since shown they are far more extensive than anyone first thought. The Zechstein evaporites are economically important: they host potash deposits, influence oil and gas reservoir behavior, and supply raw gypsum for construction across Central Europe.
North American Deposits
North America holds some of the most famous gypsum accumulations on the planet. The Permian Basin of west Texas and southeastern New Mexico contains thick evaporite sequences deposited in a shallow, restricted marine setting. Within the Salado Formation’s McNutt Potash Zone, researchers have identified meter-scale cycles that record progressive evaporation: first carbonate muds, then gypsum (now replaced by anhydrite), then halite, each cycle representing one pulse of seawater drawdown.4GeoScienceWorld (GSA Bulletin). Origin of depositional cycles in a Permian “saline giant”: The Salado (McNutt zone) evaporites of New Mexico and Texas These are some of the best-studied ancient evaporites in the world and provide a template for understanding how gypsum accumulates in marine basins generally.
Further north, thick gypsum beds occur in Nova Scotia, Ontario, and across the Great Lakes region, many of them Silurian in age. Oklahoma, Iowa, and Michigan are also historically significant producers. The United States overall ranks among the top global gypsum producers, with mines scattered from coast to coast, though the largest operations tend to cluster in the arid Southwest and the Great Plains states where thick beds lie close to the surface.
The White Sands Dune Field
Perhaps the most visually striking gypsum deposit in North America sits in southern New Mexico’s Tularosa Basin. White Sands is the world’s largest gypsum dune field, a roughly 710-square-kilometer expanse of brilliant white sand. The dunes are sourced from Pleistocene-age evaporite beds along the western, upwind margin of the field.5Sedimentary Geology. Transport and mixing of eolian sand from local sources resulting in variations in grain size in a gypsum dune field, White Sands, New Mexico, USA As the ancient Lake Otero shrank in response to increasing aridity starting around 7,000 years ago, its exposed lakebed sediments were picked up by prevailing southwest winds and sculpted into dunes.6Sedimentary Geology. White Sands Dune Field, New Mexico: Age, dune dynamics and recent accumulations
Stripping away the dune surfaces digitally reveals a terraced landscape of paleo-shorelines from the lake’s stepwise retreat. Elevated bands of taller, more closely spaced dunes sit just downwind of each former shoreline, meaning the dune field grew by adding successive segments as the lake withdrew.7Aeolian Research. Definition and origin of the dune-field pattern at White Sands, New Mexico White Sands is unusual because gypsum sand grains are softer and more soluble than quartz, so maintaining a large dune field requires a steady supply from the upwind source and enough aridity that the grains don’t simply dissolve in rain.
Asia and the Middle East
Some of the oldest commercially significant gypsum deposits in Asia are found in China’s Tarim Basin, in the far northwest of the country. Thick gypsum-salt sequences in the Lower to Middle Cambrian formations there developed in depressions inherited from an even older continental rift, which created the confined, shallow-water conditions ideal for evaporite accumulation.8Marine and Petroleum Geology. Tectono-sedimentary characteristics and controlling factors of the lower-middle Cambrian gypsum-salt rocks in the Tarim Basin, Northwest China China is one of the world’s largest gypsum producers, and the Tarim Basin deposits are among its most important sources.
The Middle East is another major producer. Iran, Saudi Arabia, Oman, and the United Arab Emirates all contain vast gypsum deposits, many associated with Miocene- and Eocene-age evaporites. The Arabian Peninsula’s sabkha flats, coastal salt-encrusted lowlands, are active gypsum-producing environments today. In Saudi Arabia’s eastern province, the sabkha environment gives rise to distinctive “desert rose” formations, rosette-shaped clusters of gypsum crystals that grow in loose sand near the surface under stable chemical conditions.9Mineralogy and Chemistry of Desert Roses, Ayn Dar Area, Abqaiq, Eastern Province, Saudi Arabia. Mineralogy and Chemistry of Desert Roses, Ayn Dar Area, Abqaiq, Eastern Province, Saudi Arabia These crystal clusters incorporate sand grains as they grow, giving each “petal” a sandy, opaque texture.
Coastal Sabkhas and the Red Sea
Sabkhas, the salt-crusted tidal flats found along arid coastlines, are among the most active gypsum-forming environments on Earth today. Along Egypt’s southern Red Sea coast, satellite monitoring shows that sabkha areas have expanded measurably over the past half century, with the total extent of studied sabkhas growing from about 126 square kilometers in 1973 to roughly 142 square kilometers by 2023.10Nature / Scientific Reports. Spatial distribution of selected coastal Sabkhas along the Southern Red Sea Coast of Egypt Individual sabkhas like Marsa Abu Madd grew from about 19 to 24 square kilometers over that period. The expansion reflects shifts in coastline dynamics and groundwater conditions, and it means the production of new gypsum in these settings is ongoing and increasing.
In saline lake systems and playas worldwide, gypsum and related minerals precipitate seasonally. During hot, dry months, evaporation concentrates the brine past the gypsum saturation point, producing fresh crystals on lake floors and within the shallow subsurface.11Earth-Science Reviews. Hydrogeologic processes in saline systems: Playas, sabkhas, and saline lakes Many of these deposits are tiny compared to ancient marine evaporites, but they are geologically significant because they show gypsum formation in real time.
The Atacama Desert
Chile’s Atacama Desert, the driest non-polar environment on Earth, is blanketed in soluble salts including abundant gypsum. The gypsum appears as surface crusts roughly ten centimeters thick arranged in polygon-like patterns, as mixed mineral layers below the surface to depths of several meters, and as crystals growing in brine ponds of salars.12CATENA. Revealing the mechanisms of soil gypsum formation in the Atacama Desert through triple oxygen and hydrogen isotopes of gypsum hydration water The calcium and sulfate feeding these deposits come from two main sources. In coastal areas where marine fog penetrates inland, sea-spray aerosols supply the bulk of the raw material; isotopic studies show that soils within about 50 kilometers of the coast receive more than half their calcium and sulfur from marine aerosols.13Geochimica et Cosmochimica Acta. Isotopic evidence for the source of Ca and S in soil gypsum, anhydrite and calcite in the Atacama Desert, Chile Further inland and at higher elevations, volcanic sulfur and continental dust take over as the dominant suppliers.
The Atacama’s gypsum is also of interest to astrobiologists. Despite the extreme hyperaridity, microorganisms colonize the translucent gypsum crusts, living a few millimeters below the surface where the mineral filters out harmful ultraviolet radiation while still letting enough light through for photosynthesis.14PubMed Central. Microbial colonization of gypsum: from the fossil record to the present day These endolithic communities have even left behind fossilized biosignatures within the gypsum, offering researchers a model for how life might survive in the sulfate-rich soils of Mars.15Chemical Geology. Biosignatures and microbial fossils in endolithic microbial communities colonizing Ca-sulfate crusts in the Atacama Desert
Giant Crystals and Cave Formations
Gypsum’s ability to grow spectacularly large crystals under the right conditions is on full display in the Naica mine in Chihuahua, Mexico. The Cave of Crystals, discovered in 2000 about 290 meters below the surface, contains gypsum beams up to 11 meters long. The crystals grew from low-salinity groundwater at a temperature of roughly 55 °C, just below the point where anhydrite and gypsum have equal solubility.16Geology. Formation of natural gypsum megacrystals in Naica, Mexico At that narrow thermal sweet spot, anhydrite in the surrounding rock slowly dissolved and re-precipitated as gypsum, feeding crystal growth over hundreds of thousands of years. A shallower cave in the same mine, the Cave of Swords at about 120 meters depth, grew its crystals at a slightly lower temperature of around 47 °C, producing smaller but still impressive formations.17Geology. Determining gypsum growth temperatures using monophase fluid inclusions—Application to the giant gypsum crystals of Naica, Mexico The temperature difference between the two caves appears to have controlled both the size and the abundance of crystals in each.
Gypsum also decorates caves in less dramatic but widespread ways. In dry caves, sulfate minerals crystallize into crusts, stalactites, and delicate formations called gypsum flowers, which are curving, fibrous crystals that radiate outward from a central point.18Encyclopedia of Caves. Gypsum flowers and related speleothems Even thinner structures known as “cave cotton” and “angel hair” form under similar conditions. The sulfate in these formations can come directly from the cave’s bedrock or from the oxidation of pyrite and hydrogen sulfide, meaning gypsum speleothems can appear in caves cut through a variety of rock types, not just evaporites.
Gypsum in Ancient Egypt
Humans have quarried gypsum for construction for at least five thousand years. In ancient Egypt, gypsum was the go-to material for plaster and mortar from the late Predynastic period onward. The most extensive and varied use occurred at Amarna, the short-lived capital built by the pharaoh Akhenaten during the Eighteenth Dynasty. Archaeologists long assumed Amarna’s gypsum came from the Faiyum Depression, about 300 kilometers to the northwest, but a much larger and closer source has been identified: nearly three square kilometers of quarries on the limestone plateau just north and east of the city, dating mainly from the Old Kingdom through the New Kingdom.19Journal of Archaeological Science: Reports. Amarna gypsite: A new source of gypsum for ancient Egypt This deposit is a “gypsite,” a loose, earthy form of gypsum that could be collected from the surface without deep mining, which helps explain why gypsum plaster was so readily available in Egyptian construction.
Synthetic Gypsum and the Energy Transition
Not all of the world’s gypsum comes out of the ground. A large share of modern supply is synthetic, produced as a byproduct of scrubbing sulfur dioxide from the exhaust of coal- and lignite-fired power plants. The flue-gas desulfurization process reacts the sulfur dioxide with limestone and water, yielding calcium sulfate that is chemically identical to mined gypsum and widely used in wallboard and cement. In Poland, for example, synthetic gypsum has accounted for 60 to 75 percent of total domestic supply.20Gospodarka Surowcami Mineralnymi – Mineral Resources Management. Availability of domestic gypsum resources versus the predicted decline in synthetic gypsum production
As countries decarbonize their energy sectors, that synthetic supply is shrinking. Poland’s synthetic gypsum production is projected to fall from roughly 2.5 million metric tons in 2024 to about 0.6 million tons by 2040, a drop of more than three quarters.20Gospodarka Surowcami Mineralnymi – Mineral Resources Management. Availability of domestic gypsum resources versus the predicted decline in synthetic gypsum production Similar dynamics are playing out across Europe and North America as coal plants close. The construction industry will increasingly need to turn back to natural gypsum quarries or find alternative materials, which gives renewed economic importance to knowing exactly where mineable deposits are and how much they hold.
Microbial Life Inside Gypsum
One of the more surprising aspects of gypsum deposits is the life they harbor. Gypsum is translucent enough to let photosynthetically useful light pass through several millimeters of crystal while blocking the ultraviolet wavelengths that would otherwise sterilize the surface.14PubMed Central. Microbial colonization of gypsum: from the fossil record to the present day In extreme deserts like the Atacama, this makes gypsum crusts one of the last habitable niches. Cyanobacteria, algae, and fungi form thin green or orange bands just beneath the mineral surface, a lifestyle known as endolithic colonization. Some of these communities leave behind fossilized structures that persist long after the organisms die, preserved by the mineral matrix they lived within.15Chemical Geology. Biosignatures and microbial fossils in endolithic microbial communities colonizing Ca-sulfate crusts in the Atacama Desert
This phenomenon extends beyond the Atacama. Gypsum-hosted microbial communities have been documented in desert environments across North Africa, the Middle East, and even in cold arid settings like the Arctic. Researchers studying Mars habitability pay close attention to these communities because sulfate minerals, including gypsum, are widespread on the Martian surface, and any past or present Martian life might have used similar mineral shelters.
Less Obvious Deposits and Ongoing Formation
Beyond the headline locations, gypsum turns up in settings you might not expect. It is a common component of carbonate reservoir rocks in places like China’s Ordos Basin, where it appears as thin interlayers within dolomite sequences formed hundreds of millions of years ago.8Marine and Petroleum Geology. Tectono-sedimentary characteristics and controlling factors of the lower-middle Cambrian gypsum-salt rocks in the Tarim Basin, Northwest China It forms in volcanic hot-spring systems, in mine drainage channels where acid mine water meets limestone, and even in the walls of buildings when sulfate-laden moisture migrates through masonry. In agricultural contexts, gypsum is deliberately applied to soils as a calcium and sulfur amendment and to improve the structure of heavy clay.
New gypsum deposits are also still forming in the geologic present. Every sabkha that floods and dries with the tides, every shrinking desert lake, and every cave where sulfate-bearing water evaporates from a wall is adding to the planet’s gypsum inventory. The processes that produced the giant ancient deposits are the same ones operating in miniature today, which is part of what makes gypsum such a useful mineral for geologists: you can watch it form in real time and then use those observations to interpret deposits that are hundreds of millions of years old.