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Gypsum, according to popular opinion, is familiar and does not need to be introduced in more detail. Far from it, as only a few people are aware of the wide variety, meaning and use of the white material that can even be found in cookies and tofu.
From a chemical point of view, the matter is simple; it is calcium sulfate with two water molecules, i.e. Ca[SO₄]·2H₂O, in other words a water-containing calcium sulfate or a calcium sulfate dihydrate. But it can also be done without water. The pure calcium sulfate would be anhydrite. Gypsum and anhydrite are usually mentioned together because they often occur together in nature. If anhydrite is converted into gypsum by absorbing water, its volume increases by up to 60%. Buildings can suffer considerable damage if planning errors are made.
Mineralogically, gypsum is classified as a monoclinic crystal system. In the 10-part Mohs hardness scale, plaster ranks second, meaning it can be scratched with a fingernail. The line color is white, the fracture is shelly, as are some of the most important mineralogical key data.
When it comes to classification in mining, gypsum is classified as an industrial mineral. Here it can be mentioned in the same breath as graphite, kaolin, salt, sulfur, magnesite and others. In the production data, the "World Mining Data", which is published annually by the Federal Ministry of Finance, China ranks first in production (2024: 60,000,000 tons) followed by the USA (20,800,000 tons) and Iran (20,216,384 tons). With 698,277 tonnes, Austria lies between Greece (672,747 tonnes) and Ukraine (750,388 tonnes).
More detailed data on domestic production can be found in the 2025 mining manual under “Mine-free mineral raw materials”. These are raw materials, as we read on page 30, which are "removed from the property owner's right of disposal and may be sought out and extracted by anyone who meets certain mining law requirements." In Austria, a total of 54 employees mine gypsum and anhydrite in seven companies, both above and below ground, in Lower Austria (1 mine), Salzburg (2 mines), Tyrol (1 mine) and Styria (3 mines). In addition, there are figures for 2024 on imports and exports from the mining manual: in addition to the domestic production of 698,277 tons, there are imports of 184,673 tons and exports of 107,241 tons. A quick look back: while the production figures in 2023 were roughly comparable to 2024, they were significantly higher in 2021 (900,374 tons). Robert Holnsteiner from the Mining Section in the Federal Ministry of Finance: "The weak development of the order situation in the construction industry is also reflected in a declining mining production of gypsum. The Recycling Gypsum Ordinance created the prerequisites for the recycling of gypsum in 2024. This means that waste is recycled in the best possible way and natural deposits are protected." A landfill ban for plasterboard has also been in effect in Austria since the beginning of 2026.
This brings us to another facet of plaster. In terms of use, it's like a stand-up manderl. “Gypsum – Mineral of the Year 2026 – The “miracle mineral” Gypsum: Infinitely recyclable” is the title of the German magazine “Der Aufsicht” (issue 2/2026). There are also details here: “Gypsum is the only natural substance that can be converted back into a rock with water. By re-firing the gypsum solid that has already been used once, for example building materials and components, the cycle from solid to powder to solid can be started again and again." In addition to natural gypsum deposits, recycling is of great importance. The third aspect of gypsum production in many countries is REA gypsum. REA stands for flue gas desulfurization systems. REA gypsum is created from the reaction of sulfur in the flue gas - as in Lignite power plants are created - with limestone. In neighboring Germany, around a third of the gypsum demand is currently covered with REA gypsum. With the planned phase-out of coal use by 2038, REA gypsum production will increasingly decrease.
The driving force for Mineral of the Year 2026 was the Association of Friends of Mineralogy and Geology (VFMG). But as early as 2022, when half of German gypsum still came from REA plants, the Professional Association of German Geoscientists (BDG) had drawn attention to the situation and named gypsum rock of the year. The goal of the German geologists for Rock of the Year has a clear intention: "With the nomination for Rock of the Year, rocks that are remarkable due to their geological formation and economic importance will be brought into greater public interest."
While REA gypsum is not an issue in Austria, the "citric acid gypsum", which is produced during the production of citric acid by the Junbunzlauer company in Wulzeshofen (Lower Austria), is definitely important and is supplied to the construction industry.
The early traces of its use go back to ancient Egypt, where gypsum mortar was used on the Pyramid of Cheops. But aside from its historical significance, gypsum in its anhydrite and alabaster modifications is now ubiquitous. The latter is mainly used for sculptures and souvenirs. The advantage of the mostly beige stone is evident; it is easy to edit; However, this type of ornament should only be placed in dry indoor rooms because alabaster is water-soluble. Artists use plaster for making casts or for modeling.
Gypsum is important for the construction industry, where it is used for plasterboard or stucco. The corresponding apprenticeships are plasterer and drywall fitter. It is also found in plasters and fillers. Electricians rely on plaster to lay sockets or the like in walls. A tip: always sprinkle plaster into water, not the other way around. Quick processing is important; Plaster sets and becomes hard within five to ten minutes.
Plaster bandages are a classic for bone fractures, but are also used to stabilize fossil bones and mammoth tusks. Anyone who finds the number E 516 in food additives is dealing with calcium sulfate, i.e. gypsum. It is used as a solidifying agent or carrier, for example in the production of bread, cookies or the preparation of brewing water. Gypsum, i.e. calcium sulfate or E 516, can also be used as a substitute for table salt or as a coagulant for tofu (www.lebensmittellexikon.de).
When geologists find gypsum, one thing is clear: when it was formed, it was warm, very warm, significantly warmer than today. Gypsum and salt are evaporite rocks, which are formed by evaporation in shallow marine areas in a tropical climate and are geological climate indicators.
In Austria there are gypsum deposits in the so-called “Haselgebirge”. This formation within the Northern Limestone Alps is a rock mixture of clay, anhydrite, gypsum and rock salt that was formed at the turn of the Era (Paleozoic) to the Mesozoic (Mesozoic) around 250 million years ago. All major gypsum, anhydrite and rock salt deposits can be found here. While salt deposits dominate in the west up to the Salzkammergut, there are large gypsum deposits in the east of Austria. The “Gipsbergbau Seegrotte” show mine in Hinterbrühl (Lower Austria) is well known. While gypsum was initially mined here, the tunnels were used by the armaments industry during the Second World War; Today you can explore the eventful history of mining on a boat trip on Europe's largest underground lake.
Due to the solubility of gypsum, large amounts of gypsum can be dissolved through the seepage of rainwater. The resulting cavities can not only lead to subsidence, but also to sinkholes where large holes suddenly form. In the summer of 2013, a seven-meter-wide sinkhole in the Reutte district (Tyrol) was spectacular and appeared completely unexpectedly in the middle of a green meadow. “Sudden large hole in the ground near Reutte” was the headline on August 13, 2013 tirol.ORF.at. Lower Austria, such as Hinterbrühl or Maria Enzersdorf, where the long-forgotten Hochleiten mine was discovered underground in the Marienhöhe district following sinkholes in the 1990s, is also worth mentioning when it comes to sinkholes. (Thomas Hofmann, July 31, 2026).