Geographic Minerals



Polyhalite, a mineral sulfate found in deposits of evaporite (K2Ca2Mg(SO4)4•2H2O) that also occurs with anhydrite and halite. It crystallizes in the triclinic system although it is very rare in crystals. Standard habit is fibrous to huge. It is typically colorless, white to gray, although it’s going to be Venetian red thanks to iron oxide inclusions. Polyhalite incorporates a Mohs hardness of 3.5 and a selected gravity of 2.8.

Crystal structure of Polyhalite

A special mineral salt that can be used as a fertilizer and has potential for other industrial applications is polyhalite. Its name reflects its composition of hydrated potassium, calcium, and magnesium sulfates, from the Greek terms meaning “many salts”. It occurs in marine sedimentary evaporites and is a major potassium ore mineral in New Mexico’s Carlsbad deposits. It is also present as a 2–3% contaminant of Himalayan salt.

Polyhalite was first described in 1818 for specimens from its type locality in Salzburg, Austria. It absolutely was formed during the evaporation of prehistoric seas within the geological period. Around 260 million years ago, Boulby Mine (the world’s only polyhalite mine) sat on the sting of the Zechstein Sea. The environment’s hot and dry conditions meant that the sea evaporated faster than it could be re-filled, leaving minerals of polyhalite, halite, and potash behind. Their only connection is that both are evaporite minerals, notwithstanding the similarity in names between polyhalite and halite (the naturally occurring form of table salt).

Industrial uses for Polyhalite

It makes up 7 percent of the rock within the salt deposits at Stassfurt, Ger., and is additionally abundant within the salt deposits of the Saratov region of Russia, where certain beds contain 85 percent polyhalite. In 2010, the first polyhalite mineral mining activity began at Boulby Mine, and the mine is currently the only source of polyhalite to be sold as polysulphate by Israel Chemicals. In 2016, Sirius Minerals announced plans to construct a new polyhalite mine in the area, the Woodsmith Mine. In March 2020, Anglo American plc took over the plant.

Another notable locality is the Texas-New Mexico potash area. Small and unusual crystals; tabular {010} or elongated (001) and with several shapes. Huge in general, fibrous to foliate. Often used as a fertilizer is polyhalite, which contains four essential nutrients and is low in chloride:

  • 48% SO3 as sulfate
  • 14% K2O as from sulfate of potash
  • 6% MgO as from magnesium sulfate
  • 17% CaO as from calcium sulfate

No health risk information for this content has been entered into the database. People should always carefully handle mineral specimens.


Information Sources:

  3. wikipedia