Defined by Rieder et al. (1998) as a trioctahedral mica between, or close to, the annite- phlogopite (i.e., ferrous iron and magnesium substitutions) and siderophyllite-eastonite (i.e., Al rich) joins. The term grandfathers the use of “biotite” in the field, when a chemical analysis is unavailable to describe a dark mica, presumably without Li.