Anhydrite

Very common mineral of the sulfates class

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Beautiful anhydrite from Bleiberg, Carinthia, Austria

Origin of name: firstly discovered in 1794 by Austrian entomologist and mineral collector Nicolaus Poda von Neuhaus, who called the mineral muriacite because he erroneously thought it to contain hydrochloric acid (acidum muriaticum).

Later analyses revealed that it is water-free calcium sulphate. In 1801 French mineralogist René-Just Haüy named the mineral accordingly chaux sulfatée anhydre (water-free sulphate chalk). Two years later German chemist Martin Heinrich Klaproth confirmed that the mineral does not contain hydrochloric acid.
The name anhydrite (from Greek ἄ(ν)- á(n)-, "without", "devoid of" and ὕδωρ hýdōr, "water") was coined by German mineralogist and geologist Abraham Gottlob Werner in his Handbuch der Mineralogie (Handbook of mineralogy).
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Synonyms and trade names: anhydritespar, anhydritegypsum, karstenite (after German mineralogist Dietrich Ludwig Gustav Karsten),gekrössstein (bowel stone, because of its resemblance to the recurring folds of a bowel), muriacite, angelite (for light blue anhydrite from Peru)

Localities: in 2025 more than 1800 localities on all continents, including Antarctica, were known.
Type localities are the salt mine near Hall in Tyrol, Austria and the potassium mine near Leopoldshall, Germany

Anhydrite with pyrite and sphalerite from Bleiberg, Carinthia, Austria

Handling: due to low hardness and perfect cleavage anhydrite is not suited for use in jewellery.
Anhydrite can take up water, thus turn into gypsum and increase its volume by up to 50%. The process is reversible but nevertheless anhydrite should be kept dry.

Worth knowing: anhydrite has plenty of uses. The building material industry uses it to produce floor screed, cement and gypsum. For the chemical industry it is a source of calcium to produce fertilizer and of sulphur to produce sulphuric acid.
As E16 (short for Europe number, code for substances, synthetic or natural, used as food additives) it helps food industries to solidify tofu and canned food. It also works as a stabilizer and acidity regulator in baking mixes and as a carrier for food colourings.

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