Glauberite is a scarce sodium calcium sulfate mineral (Na2Ca(SO4)2). It forms in lacustrine or marine evaporitic settings. It has a slightly waxy, nonmetallic luster, is often clear, has a white streak, is moderately soft, and slowly dissolves in water. It is frequently encountered as a pseudomorph - other minerals have replaced the glauberite, but retained the original crystal form.
Glauberite (3.4 cm across) from the Verde Formation (Miocene-Pliocene) at the Camp Verde Salt Mine (aka Graham-Wingfield sulfate ground), a little southwest of the town of Camp Verde, central Arizona, USA. The Verde Formation consists of source-proximal siliciclastics, lacustrine carbonates & evaporites deposited in the Verde Basin, a Basin & Range graben in central Arizona that had no drainage outlet during the Miocene & Pliocene.
Some info. from:
Thompson (1983) - Campe Verde evaporites. Mineralogical Record 14(2): 85-90.