A porphyroblast is a large mineral crystal in a metamorphic rock which has grown within the finer grained matrix. Porphyroblasts are commonly euhedral...

off from either side of the porphyroblast within the strain shadows.[citation needed] During shearing, the porphyroblast may rotate, to form a characteristic...

forms a re-entrant as it is absorbed by the growth of the andalusite porphyroblast. The cycle of growth-retardation-growth then repeats itself, creating...

purple color Greek πορφύρα (porphúra), Tyrian purple, royal purple porphyroblast post- denotes something as 'after (time)' or 'behind (space)' another...

local influences. This is a megascopic version of what may occur around porphyroblasts. Often, fine observation of foliations on outcrop, hand specimen and...

schistosity. Though not a defining characteristic, schists very often contain porphyroblasts (individual crystals of unusual size) of distinctive minerals, such...

A poikiloblast is a porphyroblast mineral with small inclusions of the previous rock in it. From the texture (if any) shown in the inclusion, the deformation...

characterized by coarse, irregular grains, including some larger grains (porphyroblasts.) Sandstone has been used since prehistoric times for construction,...

metamorphic rock characterized by an abundance of platy minerals. In this example, the rock has prominent sillimanite porphyroblasts as large as 3 cm (1.2 in)....

characterized by coarse, irregular grains, including some larger grains (porphyroblasts). In the United States, formations of quartzite can be found in some...