Hornfels is a metamorphic rock that has been
subjected to heating during contact metamorphism
close to intrusive bodies.
Hornfeld is fine-grained, sometimes banded, but can also show a porphyroblastic texture. Hornfels is non-foliated, the grains showing no orientation. Mosaic structure of the mineral grains of nearly equal dimensions are characteristic.
Depending on the distance from the pluton and on the mineralogical composition of the source rock that underwent contact metamorphosis, mineral associations and size as well as geochemical contents of hornfels are very variable.