Mineral
Anhydrite
CaSO₄Anhidrit
Gypsum without its water: a calcium sulfate mineral, whose blue-grey Peruvian form is sold as “angelite”.
Also known as: Angelite (trade name of blue-grey anhydrite from Peru)
- Popularly: Ore and raw material
- Industrial
- Important in Türkiye
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In short
Anhydrite is a mineral made of calcium, sulfur and oxygen (calcium sulfate, CaSO₄). Chemically, its only difference from gypsum is that it holds no water in its crystals; its name comes from the Greek for “without water”. It is an important mineral of the sedimentary layers left behind when salty water evaporates. In damp conditions it takes up water and turns into gypsum. A pale blue-grey, semi-transparent form from Peru is sold as an ornamental stone under the trade name “angelite”.
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How does it form?
Anhydrite is found mostly in evaporite layers, which form when salty water evaporates: it is deposited together with rock salt and gypsum on hot, dry coastal flats and in deep basins. Gypsum that formed first may lose its water as it is buried and heated, turning into anhydrite; when the anhydrite comes close to the surface again and takes up water, it turns back into gypsum. It forms the “cap rock” above salt domes. More rarely it is found around volcanic gas vents, in hot-water chimneys on the sea floor, and in hot-water ore veins.
What is it used for?
- Cement: ground anhydrite or gypsum is an additive that regulates the setting time of Portland cement.
- Building materials: it is used in plasters, mortars and other building products.
- Agriculture and chemistry: it serves as a soil improver and fertiliser, and as a source of sulfur for making sulfuric acid.
- Filler: it is used as a filler in paints, plastics, rubber and coatings.
- Ornamental stone: the blue-grey, semi-translucent “angelite” is cut into cabochons and beads. Being soft, it scratches easily.
In Türkiye
Türkiye’s evaporite deposits, especially gypsum, anhydrite, halite and selenite, are widespread in its Tertiary sedimentary basins. According to a study published in 2023 in the Çukurova University Journal of the Faculty of Engineering, anhydrite layers up to 300 metres thick have been found in the evaporite deposits of the Sivas Basin. In 2022 about 600,000 tonnes of gypsum were quarried from five licensed sites in the basin, and about 45 per cent of it went to cement plants. Anhydrite itself is not mined; at the gypsum quarries it is left in the lower layers, and the study says that its use in Türkiye is almost negligible.
What determines its value?
In industry, anhydrite’s value depends on its calcium sulfate content (purity), the thickness and size of the deposit, its distance from users such as cement plants, and the cost of mining it. As an ornamental stone, “angelite” is judged by evenness of colour, translucency and quality of polish; it is soft, so it needs careful handling in jewellery. Collectors look for clear, well-formed crystals from places such as the Simplon Tunnel.
This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment.
How to recognise it
- 1
When broken it splits in three directions at roughly right angles, giving cube-like fragments.
- 2
It is harder than gypsum (hardness 3–3.5): a fingernail scratches gypsum but not anhydrite. Its specific gravity (about 2.97) is also higher than gypsum’s (about 2.3).
- 3
It is colourless, white, or tinted pale blue or violet; cleavage surfaces look pearly, other surfaces glassy or greasy.
- 4
It is most common as layers, masses or fibrous aggregates; well-formed crystals are rarer.
- 5
Left in contact with water or damp air, it gradually takes up water and turns into gypsum.
Fakes and imitations
What shops usually don’t tell you:
- The stone sold as “angelite” is pale blue-grey anhydrite from Peru; it is a trade name, not a separate mineral, and should not be confused with celestine.
Myths and misconceptions
MythAngelite is a kind of celestine.
FactThe blue-grey stone sold as angelite is anhydrite, not celestine. Its colour and trade name sometimes lead to it being mentioned alongside celestine, but it is calcium sulfate, whereas celestine is strontium sulfate.
MythAnhydrite and gypsum are the same thing.
FactGypsum contains water in its crystals (CaSO₄·2H₂O); anhydrite does not (CaSO₄). Anhydrite is harder and heavier, and because it swells as it turns into gypsum on taking up water, it can lift the ground.
What is it believed to be good for?
This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.
The meanings people give this stone, and who holds them:
- Today, crystal-therapy practitioners claim that the blue anhydrite sold as “angelite” is calming and soothes fear, anger and anxiety.
- The same circles say angelite increases spiritual awareness and makes it easier for a person to express themselves.
What science says
“Angelite” is a trade name for blue-grey anhydrite from Peru; there is no scientific evidence that it calms people or raises spiritual awareness. Anyone with lasting anxiety or anger problems should see a professional. Anhydrite is not a poisonous mineral, but when it meets water it begins to turn into gypsum and breaks down, so it should not be soaked in water or used to make “gem water”.
Did you know?
Anhydrite was first found in 1794 in a salt mine near Hall in Tirol, Austria.
In Staufen im Breisgau, Germany, a geothermal drilling project in 2007 let groundwater reach a layer of anhydrite beneath the town; pockets of anhydrite turned into gypsum, the ground swelled over a wide but uneven area, and buildings were damaged.
The giant gypsum crystals of the Cave of the Crystals in Mexico’s Naica Mine grew very slowly after the cave water cooled below 56 °C and the anhydrite dissolved; the largest crystal is 11.4 metres long.
Where is it found?
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- Hall in Tirol, Tyrol, Austria · Type localityThe mineral was first discovered in 1794 in a salt mine here
- Staßfurt-Leopoldshall, Saxony-Anhalt, Germany · Historic sourceA salt and potash district listed by the Handbook of Mineralogy for anhydrite
- Hallein, Salzburg, Austria · Historic sourceA Salzburg town known for its salt mines; listed by the Handbook of Mineralogy for anhydrite
- Simplon Tunnel, Valais, Switzerland · Known localityAccording to the Handbook of Mineralogy, tunnelling produced clear, gemmy anhydrite crystals
- Naica, Chihuahua, Mexico · Known localityThe mine with the Cave of the Crystals, where anhydrite dissolved in cooling water and gypsum crystallised in its place
- Carlsbad potash district, Eddy County, New Mexico, USA · Major depositAccording to the Handbook of Mineralogy, large anhydrite deposits occur here
- Salt Range, Punjab, Pakistan · Known localityA range with large rock-salt mines; the Handbook of Mineralogy lists anhydrite from the Salt Range (the point lies near Khewra, in the eastern part of the range)
- Sivas Basin, Türkiye · Major depositAnhydrite beds up to 300 metres thick have been found in the basin’s evaporites; only gypsum is mined in the basin, not anhydrite
Locations are approximate to protect sites. Red dots mark places in Türkiye. Open in the big map →
Frequently asked questions
What is anhydrite?
Anhydrite is a mineral made of calcium, sulfur and oxygen (calcium sulfate, CaSO₄). Chemically, its only difference from gypsum is that it holds no water in its crystals; its name comes from the Greek for “without water”. It is an important mineral of the sedimentary layers left behind when salty water evaporates. In damp conditions it takes up water and turns into gypsum. A pale blue-grey, semi-transparent form from Peru is sold as an ornamental stone under the trade name “angelite”.
What is anhydrite used for?
Cement: ground anhydrite or gypsum is an additive that regulates the setting time of Portland cement. Building materials: it is used in plasters, mortars and other building products. Agriculture and chemistry: it serves as a soil improver and fertiliser, and as a source of sulfur for making sulfuric acid. Filler: it is used as a filler in paints, plastics, rubber and coatings. Ornamental stone: the blue-grey, semi-translucent “angelite” is cut into cabochons and beads. Being soft, it scratches easily.
How hard is anhydrite?
It has a hardness of 3–3.5 on the Mohs scale. A fingernail cannot scratch it, but a steel knife can. Its specific gravity is 2.95–2.98 g/cm³.
Where is anhydrite found?
Its best-known localities: Hall in Tirol, Tyrol, Austria; Carlsbad potash district, Eddy County, New Mexico, USA; Sivas Basin, Türkiye; Staßfurt-Leopoldshall, Saxony-Anhalt, Germany; Hallein, Salzburg, Austria.
Where is anhydrite found in Türkiye?
Known localities in Türkiye: Sivas Basin, Türkiye.
How can you tell if anhydrite is real?
When broken it splits in three directions at roughly right angles, giving cube-like fragments. It is harder than gypsum (hardness 3–3.5): a fingernail scratches gypsum but not anhydrite. Its specific gravity (about 2.97) is also higher than gypsum’s (about 2.3). It is colourless, white, or tinted pale blue or violet; cleavage surfaces look pearly, other surfaces glassy or greasy. The stone sold as “angelite” is pale blue-grey anhydrite from Peru; it is a trade name, not a separate mineral, and should not be confused with celestine.
Is anhydrite valuable?
On the “street to diamond” value ladder it sits on step 3 of nine: Building and industrial stone. In industry, anhydrite’s value depends on its calcium sulfate content (purity), the thickness and size of the deposit, its distance from users such as cement plants, and the cost of mining it. As an ornamental stone, “angelite” is judged by evenness of colour, translucency and quality of polish; it is soft, so it needs careful handling in jewellery. Collectors look for clear, well-formed crystals from places such as the Simplon Tunnel.
What is anhydrite good for?
Today, crystal-therapy practitioners claim that the blue anhydrite sold as “angelite” is calming and soothes fear, anger and anxiety. The same circles say angelite increases spiritual awareness and makes it easier for a person to express themselves. “Angelite” is a trade name for blue-grey anhydrite from Peru; there is no scientific evidence that it calms people or raises spiritual awareness. Anyone with lasting anxiety or anger problems should see a professional. Anhydrite is not a poisonous mineral, but when it meets water it begins to turn into gypsum and breaks down, so it should not be soaked in water or used to make “gem water”. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.
Sources
- Anhydrite · Wikipedia
- Handbook of Mineralogy: Anhydrite · Mineralogical Society of America
- Anhidrit · Vikipedi
- Economically the Sivas Basin Natural Anhydrite Potential, Reserve Estimation and Geochemical Characteristics, Central Anatolia, Türkiye (Z. Duran, O. Canbaz), Çukurova Üniversitesi Mühendislik Fakültesi Dergisi 38 (2), 421–431 · Çukurova Üniversitesi, 2023
- Cave of the Crystals · Wikipedia
- Staufen im Breisgau · Wikipedia
External links
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