aphanitic

/ ăf′ə-nĭt′ĭk /

1. Of or relating to an igneous rock in which the crystals are so fine that individual minerals cannot be distinguished with the naked eye. Aphanitic rocks are extrusive rocks that cooled so quickly that crystal growth was inhibited.
2. Compare phaneritic

Example Sentences

“I can tell you something ‘bout an aphanitic.”

From New York Times

Hence, any rock which is compact, crystalline and fine grained, is frequently said to be aphanitic, without implying exactly to which of the principal rock groups it really belongs.

From Project Gutenberg

There is greater variety in texture, from fine aphanitic traps up to coarse grained dolerites with feldspars one-third of an inch long.

From Project Gutenberg