Glauberite is a monoclinic sodium calcium sulfate mineral with the formula Na2Ca(SO4)2.

It was first described in 1808 for material from the El Castellar Mine, Villarrubia de Santiago, Toledo, Castile-La Mancha, Spain.

It occurs associated with halite, polyhalite, anhydrite, gypsum, thenardite, mirabilite, sassolite and blodite.

[4] Because of its solubility, glauberite is often dissolved away from the crystal matrix leaving a distinctly shaped hollow cast.

Gypsum pseudomorphs are common due to increased humidity.