Equidimensional (geology)

In geology, the term "equidimensional" describes a grain, crystal, or other geological feature that has approximately equal dimensions in all directions. In simpler terms, it is roughly the same size in length, width, and height. This is in contrast to features that are elongated (tabular or rod-shaped) or flattened (platy).

Equidimensionality is a descriptive property, often used in the characterization and classification of sedimentary rocks, igneous rocks, and metamorphic rocks. It helps in understanding the formation processes and history of these rocks. For example, the presence of a high proportion of equidimensional grains in a sandstone might indicate a different depositional environment compared to a sandstone dominated by elongated grains.

The term is often used qualitatively, based on visual inspection. However, quantitative methods, involving measurement of grain axes, can also be employed to assess the degree of equidimensionality. The ratio of the longest axis to the shortest axis is a common metric used to quantify grain shape. Lower ratios indicate a higher degree of equidimensionality.