Orthorhombic Iron Disulphide (Marcasite) sometimes shows cyclic groups of five individuals, bounded by ∞ P, {110} (M); P∞̆, {011} (l); and 0P, {001}, and united into a pentagonal figure by (M) as twinning plane.

Marcasite

Orthorhombic Iron Disulphide (Marcasite) sometimes shows cyclic groups of five individuals, bounded…