☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2
The anthophyllite group are orthorhombic amphiboles in the magnesium-iron-manganese amphibole subgroup. The minerals in this root name group may have either Pnma or Pnmn (proto- prefixed name) space-group symmetry. The anthophyllite group's general composition is defined with A(Na+K+2Ca)<0.5 apfu and C(Al+Fe3++2Ti)<1 apfu.
Ferro-anthophyllite has a standard Pnma space-group symmetry and is defined with Fe as the dominant element both in the B and C positions.