Anhydrraatit

Anhydrite is a mineral species composed of hydrated calcium sulfate, with the chemical formula CaSO4·2H2O. It is a relatively common mineral, found in a variety of geological settings, and is known for itsogginess when cut into slabs.

Anhydrite has a monoclinic crystal system, and typically appears as a white or transparent to yellowish mineral. Its hardness is around 3 on the Mohs scale, and it has a vitreous luster. In addition to its presence in sedimentary rocks, anhydrite has also been identified in hydrothermal veins, contact metamorphic rocks, and in cavities of igneous and metamorphic rocks.

When anhydrite undergoes heating or dehydration, it converts into the mineral anhydrite (CaSO4), which has been known to cause difficulties in some construction projects, as the mineral often expands significantly as it dehydrates. Because of this unique property, anhydrite can lead to cracking and spalling in affected structures.

Chalk and gypsum deposits are often formed from the remains of anhydrite that has undergone diagenesis, where the sulfate content of sea water was precipitated in acidic hot water environments. Additionally, anhydrite is associated with other evaporites such as halite and siliceous aggregates.

Anhydrite can be found in many parts of the world, with significant deposits discovered in the Middle East in Syria and Iraq, and in Europe including Portugal, Oklahoma, and Egypt. Mining for anhydrite often seeks to extract its associated evaporate minerals, which are of economic interest for industrial and construction purposes.