Hornfels

Horn clif are completely recrystallized metamorphic rocks. They occur at 600 to 700 ° C. At these temperatures the shale rocks lose their Schiefrigkeit and take part in the so-called hornfels structure, thereby forming quartz and feldspar a directionless structure. The dense and hard, compact rock has fine to medium grain size and varies in color depending on the parent rock of white, gray, green, blue and black and is usually spotted. Hornfels produced by contact metamorphism of silicate and / or oxide precursors.

Mineral constituents

Depending on the starting material variable:

• Andalusite, cordierite, biotite, muscovite, quartz in pelites;
• Diopside, grossular, vesuvianite, epidote in marl / calcareous marl.

Naming, varieties and use

This material occurs primarily in the Thuringian Forest and resin. The name hornfels derived from the German miners' language.

Varieties are garnet hornfels, chiastolite - hornfels, pyroxene hornfels and cordierite hornfels, further Tonschieferhornfels and greywacke hornfels.

Horn clif be used as gravel and road construction materials. The hand ax from Stedebergen, which was found in a Weser- gravel pit is made of Tonschieferhornfels. Due to its good sound quality hornfels was from Cumbria, England, used in the 19th century for the production of a Lithophons, the Musical Stones of Skiddaw.