orthorhombische

Orthorhombische refers to the orthorhombic crystal system, one of the seven crystal systems used in crystallography. In this system the crystal is based on three mutually perpendicular axes a, b, and c, each of which generally has a different length. All interaxial angles are 90 degrees, so the unit cell is a rectangular parallelepiped with unequal edge lengths (a ≠ b ≠ c).

In the orthorhombic system, there are three Bravais lattice types: primitive (P), base-centered (C), and body-centered (I). These lattices describe how lattice points are arranged within the unit cell. The system supports a range of symmetry operations, leading to multiple space groups and crystal classes, with the highest common point-group symmetry around orthorhombic mmm (D2h).

Physical properties of orthorhombic crystals are typically anisotropic, meaning properties such as refractive index, thermal expansion, and mechanical stiffness vary along the crystallographic a, b, and c directions. Optical behavior is biaxial, often displaying three distinct refractive indices (nα, nβ, nγ). Cleavage tends to occur along the coordinate planes, and external morphology frequently shows rectangular or blocky prismatic forms aligned with the orthorhombic axes.

Common minerals and materials with orthorhombic symmetry include olivine (forsterite-fayalite series), barite, and topaz, among others. The system is also relevant in metallurgy and mineralogy for describing crystal habits and diffraction patterns.

Orthorhombic crystals are distinguished from tetragonal crystals, which have a equal a and b axis (a = b ≠ c), and from monoclinic crystals, which have one oblique angle. Identification commonly relies on X-ray diffraction patterns, which reveal the 90-degree interaxial angles and distinct lattice parameters.