"Fishtail" Selenite / Gypsum Specimen - Sierra Mojada, Mexico variscite The distinctive layers were formed

The distinctive layers were formed in ancient oceans as dissolved iron reacted with oxygen produced by early microorganisms (cyanobacteria)

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This variety of gypsum

"Fishtail" Selenite / Gypsum Specimen - Sierra Mojada, Mexico variscite The distinctive layers were formedSelenite, a type of gypsum, is a hydrous calcium sulfate (CaSO42H2O) that forms monoclinic crystals with prismatic or bladed shapes and distinct rhombic appearance. It can also be found as arrowhead shaped twins with beveled edges. While pure selenite is colorless or white, impurities can result in shades of pale gray, yellow, red, and brown. With a hardness of 1. 5 2. 0, selenite is transparent to translucent and has a vitreous to pearly luster. It