hornblende-hornfels facies

geology

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June 29, 2026

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The hornfels facies is a classification of metamorphic rocks formed by contact metamorphism. This occurs when heat and fluids from igneous intrusions alter surrounding rocks, creating a hard, fine-grained rock called hornfels. Temperatures can reach up to 800° C (1,470° F). The specific minerals in hornfels depend on the original composition of the parent rock.1

The hornblende-hornfels facies represents a deeper level of contact metamorphism with pressures of a few kilobars. It is characterized by the stability of hydrated minerals and can show a transition towards regional metamorphism. These rocks often develop a "spotted" texture, with new minerals growing on pre-existing ones, typically found near large granite batholiths.2

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metamorphic rock
Hornblende-hornfels facies
A generally deeper level of contact metamorphism at pressures of a few kilobars is represented by the hornblende-hornfels facies. Hydrated phases become stable, and the transition to regional metamorphism becomes apparent. Because of the generally greater depth, this type of aureole is often…
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A generally deeper level of contact metamorphism at pressures of a few kilobars is represented by the hornblende-hornfels facies. Hydrated phases become stable, and the transition to regional metamorphism becomes apparent. Because of the generally greater depth, this type of aureole is often…
Read More