equigranular

Equigranular is a descriptive term used in geology, petrology, and materials science to denote a texture or microstructure in which the constituent grains or crystals are approximately the same size throughout a rock or polycrystalline material. The term emphasizes uniformity of grain size rather than shape or orientation.

In geology and petrography, equigranular textures are often observed in igneous and metamorphic rocks where crystallization or recrystallization occurred under relatively uniform conditions. Rock bodies with equigranular groundmasses lack prominent oversized crystals (phenocrysts) and display a uniform grain size across the rock. This texture is commonly contrasted with porphyritic textures, where large crystals are embedded in a finer-grained matrix, and with inequigranular textures, which show a wide range of grain sizes.

In metamorphic rocks, equigranular or granoblastic textures indicate that mineral grains have grown to similar sizes during metamorphism, producing a mosaic-like fabric with homogeneous grain dimensions. The term helps distinguish rocks and fabrics that can appear similar in mineralogy but differ in how uniformly their grains have grown or recrystallized.

In materials science and engineering, equigranular describes polycrystalline materials in which the grains are of similar size, contributing to more isotropic mechanical properties. Processing methods such as controlled annealing, recrystallization, or homogenization can promote equigranular structures, which are often desirable for uniform strength and ductility. The concept is closely related to grain-size distribution and to the broader idea of a uniform microstructure.

See also: grain size, porphyritic, inequigranular, granoblastic, equiaxed.