hardening of rocks by heat or baking; also the hardening of sediments through cementation or compaction, or both, without the introduction of heat. The classic example is the rock called hornfels (hornfels facies), which is formed at contacts with igneous intrusions and in which heat and fluids from the intruding magma reconstitute the original wall rock into a hardened, flinty rock with a dense texture; it also is commonly formed by induration of carbonate sedimentary rocks and shales.