hypidiomorphicgranular

Hypidiomorphic granular is a texture descriptor used in petrology and mineralogy to characterize rocks in which the constituent mineral grains are largely granular, yet many grains exhibit partial euhedral development. The term combines hypidiomorphic, meaning crystals show some well-formed faces on at least part of their surfaces, with granular, indicating a matrix of rounded to polyhedral grains.

In a hypidiomorphic granular rock, individual crystals are not completely euhedral or completely anhedral. Instead, they display a mix: some faces are well developed while other faces are irregular or indistinct. This results in a fabric that appears granular at the hand specimen or thin section scale, but with occasional visible crystal faces indicating partial crystal perfection.

The texture implies growth under conditions that allow limited but not uniform crystal development. Factors such as space constraints, fluctuating crystallization rates, or subsequent tectonic or metamorphic processes can preserve or reveal partial euhedral faces on otherwise granular grains. Minerals commonly described with this texture include feldspars and other framework-forming minerals in magmatic and some metamorphic rocks, though the term can apply to multiple mineral species.

Usage notes: hypidiomorphic granular is a descriptive, not a strictly quantitative category. It helps convey that grains are not purely granular nor entirely euhedral, but occupy an intermediate end of crystal development. As with other texture terms, its interpretation benefits from complementary observations of mineralogy, grain size, and the rock’s formative history.