The texture of extrusive rocks is characterized by fine-grained crystals indistinguishable to the human eye, described as aphantic.

citation

Wikipedia contributors. (2023, July 27). Extrusive rock. In Wikipedia, The Free Encyclopedia. Retrieved February 12, 2024, from https://en.wikipedia.org/w/index.php?title=Extrusive_rock&oldid=1167398989

Extrusive rock (Wikipedia) Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contrast, intrusive rock refers to rocks formed by magma which cools below the surface.