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n. pl. hornfels
A fine-grained metamorphic rock composed of quartz, feldspar, mica, and other minerals, formed by the metamorphism of sedimentary rocks from heat associated with magma.
[German : Horn, horn; see hornblende + Fels, rock, cliff (from Middle High German vels, from Old High German felis).]
(Geological Science) a hard compact fine-grained metamorphic rock formed by the action of heat from a magmatic intrusion on neighbouring sedimentary rocks. Also called: hornstone
[German: literally, horn rock]
a dark fine-grained metamorphic rock, the result of recrystallization of siliceous or argillaceous sediments by thermal metamorphism.
[1850–55; < German, =Horn horn + Fels rock, cliff]
A type of granular, fine-grained metamorphic rock.