Dietary supplements may utilize sodium selenite, L-selenomethionine or selenium-enriched yeast. Gypsum also crystallizes as translucent crystals of selenite. The selenous acid is neutralized to form sodium selenite. Crystals of the mineral selenite are fairly common in places, as are nodules of pyrite. Selenate is the least reduced, followed by selenite, and elemental selenium. Tellurite dianion is pyramidal, like selenite and sulfite. Below that is a layer of selenite containing 94-96% calcium sulphate. It reacts with base to form selenite salts containing the anion. Some selenite and satin spar specimens exhibit fluorescence or phosphorescence. These include silver selenite (AgSeO) and sodium selenite (NaSeO). Glutathione is directly involved in the reduction and assimilation of selenite into selenocysteine. These four varieties of gypsum may be grouped together and called selenite. The quartz wedge or selenite plate enables this. This process also plays a role in the formation of selenite crystals that visitors covet. Though sometimes grouped together as "selenite", the four crystalline varieties have differences.