出典:Wiktionary
phenocryst (複数形 phenocrysts)
出典:Wikipedia
出典:『Wikipedia』 (2011/05/15 16:00 UTC 版)
A phenocryst is a relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of a porphyritic igneous rock. Phenocrysts often have euhedral forms either due to early growth within a magma or by post-emplacement recrystallization.