anhedral

views updated May 08 2018

anhedral (allotriomorphic) A morphological term referring to grains in igneous rocks which have no regular crystalline shape. Anhedral forms are developed when a crystal's free growth in a melt is inhibited by the presence of surrounding crystals. The shape of the growing crystal is thus controlled by the arrangement and orientation of the surrounding pre-existing crystals. Compare EUHEDRAL.

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