porphyroclast
/ˈpɔːfɪrəklɑːst/ /ˈpɔːfɪrəklast/Geology
noun
A relatively large grain remaining in a finer groundmass in a rock which has undergone dynamic metamorphism.
Origin
1930s; earliest use found in Journal of Geology. From porphyro- + -clast, after porphyroclastic.