A theory about a mineral with this anion (“AN-eye-on”) claims that it forms from a three-stage self-aggregation of bassanite, which also has this anion. It’s not hydroxide, but jarosite is a common iron precipitate with this anion formed from acid mine drainage. Minerals with this anion sometimes appear in so-called “desert rose” formations when found in (-5[1])arid sandy environments. Along with (-5[1])carbonates, minerals with this polyatomic anion are the most common (*) marine evaporites. (-5[2])Barite contains this anion that is found in the primary mineral constituent of New Mexico’s white sand dunes. Plaster of paris (-5[1])is formed (10[1])from heating a polymorph of anhydrite with this anion that defines a 2 on the Mohs mineral hardness scale. (10[1])Along with calcium, (-5[1])gypsum contains this anion. Epsom (-5[1])salt comprises magnesium and—for 10 points—what (10[1])anion with chemical formula SO4 2- ■END■ (10[6])