Distinctive features:  
Hard, compact rock that breaks into splintery fragments. Mineral content is variable. Found in zones of contact metamorphism.

Colour: 
Dark to medium grey.

Texture and granularity: 
Hornfelsic and fine-grained, sometimes with porphyroblastic crystals.

Composition:
Dependent on parent rock.

Field associations: 
Zone or aureole of contact metamorphism bordering granitic intrusions.

Varieties:
Cordierite hornfels, which contains crystals of cordierite; andalusite hornfels, which contains crystals of andalusite; pyroxene hormfels, which contains crystals of pyroxenel and sillimanite hornfels, which contains crystals of sillimanite.

 

Worldwide.

 

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