hornfels
horn·fels
noun
1.
a fine-grained metamorphic rock formed by the action of heat on clay rocks
Origin
Borrowed from German Hornfels, literally "horn stone", after its frequent association with glacial "horn peaks" in the Alps.
Related words
Broader terms
WordNet 2.1 (Princeton University). Wiktionary (CC BY-SA). WordNet 2.1 Copyright Princeton University. All rights reserved. Wiktionary content is available under the Creative Commons Attribution-ShareAlike Licence.