(ˈfeɪkəˌlɪθ) n (Geological Science) geology a layer of igneous rock, which has the structure of a lens, and which occurs in an invasive position in sedimentary rock
phacolith
phacolith
[′fak·ə‚lith] (geology) A minor, concordant, lens-shaped, and usually granitic intrusion into folded sedimentary strata.