Fruchtschiefer is a local variety of contact
metamorphic rock that is derived from
argillite.
Formation and mineral content
Fruchtschiefer is formed under very low pressure (low grade metamorphic rock) and temperatures of ca. 500 °C. At these temperatures
cordierite grows to the size of grains of corn, which is where its name comes from; ''Frucht'' being German for "corn" (as well as "fruit"). It contains the following minerals:
cordierite,
muscovite,
potassium feldspar,
quartz,
biotite
Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more alumino ...
and
hornblende.
Occurrence
Fruchtschiefer occurs in Germany as contact metamorphic rock in the
Harz,
Ore Mountains,
Odenwald
The Odenwald () is a low mountain range in the German states of Hesse, Bavaria and Baden-Württemberg.
Location
The Odenwald is located between the Upper Rhine Plain with the Bergstraße and the ''Hessisches Ried'' (the northeastern section ...
and
Vogtland. The best known deposits are those near
Theuma and
Tirpersdorf. Their
protoliths originate from the
Ordovician period. Rocks quarried here have been used well beyond the local region.
[Heiner Siedel, Ferdinand Heinz: ''Der Abbau von Fruchtschiefer im Gebiet um Theuma und Tirpersdorf im sächsischen Vogtland und seine Verwendung''. in: Veröffentlichungen des Museums für Naturkunde Chemnitz, vol. 44 (2021) pp 87–124.]
Use
The main traditional application is in the form of rough split masonry products of a wide variety. Fruchtschiefer from Theuma is also split or ground for use as facade slabs and plinth facings. Amongst the architectural components made in this material are window and door surrounds, columns and steps. Occasionally it is used for artistic or sculptural purposes. It was also used as canal lock and well covers as well as containers for
galvanised baths and acids.
The use of Theuma Fruchtschiefer can be traced back to the
Middle Ages. Examples include slabs in the crypt of
St. John's Church in
Plauen
Plauen (; Czech language, Czech: ''Plavno'') is, with around 65,000 inhabitants, the fifth-largest city of Saxony, Germany after Leipzig, Dresden, Chemnitz and Zwickau, the second-largest city of the Vogtland after Gera, as well as the larges ...
(built 1122), which date to the 14th century.
References
Bibliography
*
Georg Dehio
Georg Gottfried Julius Dehio (22 November 1850 in Reval (now Tallinn), Governorate of Estonia, Russian Empire – 21 March 1932 in Tübingen), was a Baltic German art historian.
In 1900, Dehio started the "''Handbuch der deutschen Kunstgesch ...
: ''Handbuch der Deutschen Kunstdenkmäler, Sachsen''. Munich, Berlin (
Deutscher Kunstverlag) 1990
* Carl Gäbert, Alexander Steuer, Karl Weiss: ''Die nutzbaren Gesteinsvorkommen Deutschlands''. Berlin (Union Dt. Verl.ges) 1915
* Horst Fröhlich (Red.): ''Plauen und das mittlere Vogtland''. Werte unserer Heimat Vol. 44. Berlin (Akademie-Verlag) 1986
* Walter Maresch, Olaf Medenbach: ''Gesteine.'' p. 252, Mosaik Verlag, Munich, 1987, {{ISBN, 3-576-10699-5.
Metamorphic rocks