or many feet in diameter. Less frequently, aplite forms stocks or bosses, or occupies the edges or irregular portions of the interior of outcrops of granite. Syenite-aplites consist mainly of alkali feldspar; the diorite-aplites of plagioclase; there are nepheline-bearing aplites which intersect some elaeolite-syenites. In all cases, they bear the same relation to the parent masses. By increase of quartz, aplites pass gradually, in a few localities, through highly quartzose modifications into quartz veins. References Felsic rocks Phaneritic rocks Plutonic rocks Subvolcanic rocks