Geology

Cubic Crystal System – Normal (Holohedral) Class The cubic crystal system (also called the isometric system ) is one of the most symmetrical systems in crystallography. It has three mutually perpendicular axes of equal length , meaning all crystallographic axes (a, b, c) are identical. The normal class (also called the holohedral class or hexakisoctahedral class ) is the most symmetrical class within the cubic system, with fourfold, threefold, and twofold rotational symmetry axes, mirror planes, a center of symmetry, and an inversion center . Symmetry Elements of the Cubic Normal Class (Galena type) The normal class of the cubic system exhibits the highest degree of symmetry, including: Rotational Axes: 3 Fourfold axes (C₄) along the principal crystallographic axes (x, y, z). 4 Threefold axes (C₃) along the body diagonals of the cube. 6 Twofold axes (C₂) along the face diagonals of the cube. Mirror Planes (m): 9 mirror planes are present. 3 are perpendicular t...