Geology. Having or designating a structure (of igneous rocks) in which minute crystals of one mineral are arranged in radiating aggregations round…

Geology. Of the structure or texture of a rock (now only an igneous rock): containing small crystals of one mineral enclosed within crystals of…

characterized by or having needle-like microlites embedded in a glassy ground-mass.

Of the structure or texture of a metamorphic rock: containing small crystals of an original mineral enclosed within crystals of its metamorphic…