What is the difference between Gypsum and Anhydrite?
Anhydrite is formed from dehydrated gypsum or to make it easier to understand when water is added to anhydrite it becomes gypsum as we can see from their chemical formulas
[Anhydrite (CaSO4) and Gypsum (CaSO4-2H2O)].
Sandstone consists of grains of quartz or feldspar or a mixture of those, cemented together by some mineral such as silica, calcite, gypsum, hematite, limonite, feldspar, anhydrite, barite, clay minerals, or zeolite that has formed between the grains. Sandstone may also contain small amounts of other minerals that were present in the sand, such as muscovite, biotite, olivine, pyroxene, and corundum. In short: quartz or feldspar or both, and calcite, gypsum, hematite, limonite, feldspar, anhydrite…