Glauberite - Na₂Ca(SO₄)₂

Habit: Gray, yellowish or colorless. Prismatic, tabular or dipyramidal crystals. Vitreous, waxy or pearly luster; transparent to translucent. White streak.

Environment: A common constituent of continental and marine evaporite deposits. Also occurs as sublimates around fumaroles, in mineral-filled cavities in basaltic lava and in nitrate deposits in arid climates.

Etymology: From its similarity in composition to Glauber’s salt, which was named after Johann Rudolph Glauber (1603-68), a German alchemist.