Megacryst

In geology, a megacryst is a crystal or grain that is considerably larger than the encircling matrix.

They are found in igneous and metamorphic rocks.

[1] Megacrysts can be further classified based on the nature of their origin, either as:[2]

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Megacrystic porphyroblasts in metasomatised Quartenschiefer (metapelitic unit in the Alps)