Palegreen aggregates of foliated schröckingerite crystals with colourless aggregates of hexahydrite coated with colourless, transparent gypsum from Rožná dump, shaft Bukov 2, Vysočina region, Moravia, Czech Republic (Field of view: 5.8 mm) — Photo: BLFrank · CC BY-SA 4.0
Hexahydrite
Natural magnesium sulfate hexahydrate — the mineral form of the heptahydrate's less-hydrated sibling.
Intro adapted from Wikipedia (CC BY-SA).
Hexahydrite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Mg(SO₄)·6H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c). It is a member of the Hexahydrite structural group.
Key properties: Mohs hardness 2–2.5; specific gravity 1.757; Pearly to vitreous luster; optically biaxial.
IMA symbol Hhy, grandfathered status — known before the IMA’s founding, named in 1911.
By dehydration of epsomite; as efflorescences on magnesian rock exposures and in mine workings; as speleothems in caves; may be widespread as an evaporative precipitate in saline lakes and soils; rarely a fumarolic precipitate.
It is found associated with Epsomite, siderotil.
With the Greek prefix, hexa, in recognition of a magnesium sulfate hydrate with six essential water molecules.