My sample collection

"Vein of gypsum and anhydrite"

From: Lime and cement mines of Baulmes (Vaud, Switzerland)
Mineral(s): Gypsum (on the left) : CaSO4 . 2(H2O)
Anhydrite (on the right): CaSO4
Age: ? Tertiary-Quaternary ?

Description: Cristals of gypsum growing in veins (grey host rock is a marly rock) and very fine cristals of rosa anhydrite. Both minerals have quite the same chemistry, except presence of water in gypsum only. On the field, they are distinguish by their hardness: low for gypsum (3), but extremly low for anhydrite (1-2, can be scratched with nail).