Hornfels (German, meaning "hornstone," after its frequent association with glacial "horn peaks" in the Alps, being a very hard rock and thus more likely to resist glacial action and form horn-shaped peaks such as Matterhorn)'s the group designation for a series of contact metamorphic rocks that've been baked and indurated by the heat of intrusive igneous masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable. Most hornfels are fine-grained, and wh… (More on Hornfels)