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hornfels

hornfels

SRI Petrography ID: 40

Names

[de] Hornfels
[en] hornfels

Description

Hornfels is a metamorphic rock that has been subjected to heating during contact metamorphism close to intrusive bodies. Hornfeld is fine-grained, sometimes banded, but can also show a porphyroblastic texture. Hornfels is non-foliated, the grains showing no orientation. Mosaic structure of the mineral grains of nearly equal dimensions are characteristic.
Depending on the distance from the pluton and on the mineralogical composition of the source rock that underwent contact metamorphosis, mineral associations and size as well as geochemical contents of hornfels are very variable.

Color

variable, depending on the source rock

Grain Size

Fine grained, sometimes porphyroblastic

Texture

massive, banded

Minerals

depending on the source rock and the metamorphosis conditions

Occurences

Harz, Eifel, Vosges, Norway

Comments

Most common hornfels types:
Biotite hornfels (from shales, slates, clays)
Calcite-silicate-hornfels (from impure limestone)
Feldspar-hornblende-pyroxene hornfels (from basalt, diabase, andesite)

Classification

Class

METAMORPHIC ROCKS

Broader Terms

igneous protolith

Homonyms

hornfels (sedimentary protolith)