aph·a·nite 
(ăfə-nīt′)
(ăfə-nīt′)n.
A dense, homogeneous rock with constituents so fine that they cannot be seen by the naked eye.
[From Greek aphanēs, unseen : a-, not; see A-1 + phainesthai, phan-, to appear, passive of phainein, to show; see PHENOMENON.]
aph′a·nitic (-nĭtĭk) adj.