porphyroblast
Sign in to savethumb|300px|Thin section of a garnet porphyroblast (black) in a mica schist that contains foliated trails of small inclusions (white and grey)
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thumb|300px|Thin section of a garnet porphyroblast (black) in a mica schist that contains foliated trails of small inclusions (white and grey)
A porphyroblast is a large mineral crystal in a metamorphic rock which has grown within the finer grained matrix. Porphyroblasts are commonly euhedral crystals, but can also be partly to completely irregular in shape.