Mica The mica group of sheet silicate minerals includes several closely related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. Wikipedia https://en.wikipedia.org/wiki/Mica Added to support Critical Zone Observatory (CZO) data use cases. ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables.