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Hornfels identification and geology

A fine-grained, massive, non-foliated metamorphic rock produced by contact metamorphism in the aureole surrounding an igneous intrusion. Hornfels is extremely hard and tough, breaking with a conchoidal or splintery fracture, and is composed of an interlocking mosaic of equigranular crystals formed by recrystallization at high temperatures. It can contain diagnostic contact metamorphic minerals such as andalusite, cordierite, and garnet. Field: petrology. Example: Spotted hornfels from the Skiddaw aureole in the English Lake District contains dark porphyroblasts of cordierite and andalusite in a fine-grained matrix, formed by the baking of mudstone adjacent to a granite intrusion.. Related terms: Contact metamorphism, Aureole, Andalusite, Skarn.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.027557+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Hornfels mean in geology?
A fine-grained, massive, non-foliated metamorphic rock produced by contact metamorphism in the aureole surrounding an igneous intrusion. Hornfels is extremely hard and tough, breaking with a conchoidal or splintery fracture, and is composed of an interlocking mosaic of equigranular crystals formed by recrystallization at high temperatures. It can contain diagnostic contact metamorphic minerals such as andalusite, cordierite, and garnet.
What is an example of Hornfels?
Spotted hornfels from the Skiddaw aureole in the English Lake District contains dark porphyroblasts of cordierite and andalusite in a fine-grained matrix, formed by the baking of mudstone adjacent to a granite intrusion.
Which earth-science field uses the term Hornfels?
Hornfels is used in petrology.
Which terms are related to Hornfels?
Related terms in this reference are Contact metamorphism, Aureole, Andalusite, Skarn.

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