A dark, fine-grained metamorphic rock consisting largely of quartz, mica, and particular feldspars.‘The slate, where thermally metamorphosed, has been turned into siliceous hornfels and mica schist.’
- ‘As a result, contact metamorphic minerals grow in random interlocking patterns giving rise to hornfels, a tough rock with no direction along which it will split preferentially.’
- ‘These are actually pseudomorphs of sericite (a fine-grained white mica) after cordierite and are found included in hornfels or slate as a product of contact metamorphism.’
- ‘For scheelite-dominated deposits, there is the formation of marbles and locally extensive tremolite, silicification, and the development of extensive skarn and hornfels zones.’
- ‘The hornfels can be very friable, as are the sakura ishi, which makes it easy to find nice crystal sections but difficult to collect matrix specimens.’
Mid 19th century from German, literally ‘horn rock’.