Class : Sulfates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal system : Monoclinic
    Chemistry : Na₂SO₄ 10H₂O
    Rarity : Common

Mirabilite (Glauber's "admirable salt") is mainly formed by the evaporation of saline solutions : it is therefore mainly an evaporitic mineral from salt lagoons in arid regions, but which is also found in the fumaroles of hot springs. Its solubility decreasing sharply with temperature, mirabilite is often deposited during the cold season along with gypsum, thenardite and glauberite. Its name comes from the expression "sal mirabile" (wonderful salt) given by the German chemist J.R. Glauber who discovered it. Mirabilite is a very fragile mineral because of its high solubility in water and its easy dehydration in a dry atmosphere. Usually transparent and colorless, it becomes white and opaque on exposure to air. It most often constitutes efflorescent encrustations, stalactites or crystalline masses ; the crystals are elongated and flattened, fibrous to acicular, sometimes short prismatic and then resembling those of pyroxenes or borax. It is a secondary sodium ore.

Main photo : Minyulite from Tom's Quarry, Kapunda, Australia © Stephan Wolfsried

Interpenetration twins are known on {100} and on {001}.

No fakes recorded for this mineral species.