GLAUBERITE
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.