Knot slate
The knotenschiefer is next to the spot slate , fruchtschiefer and the sheaf slate a variety of kontaktmetamorphen slate . Knot slate is formed at temperatures around 400 ° C and its dark color is caused by graphite. From 500 ° fruit slate is produced. Knot slate is characterized by up to centimeter-sized knots and knot-like mica layers as a result of an increase in grain size during metamorphosis . The knots consist of iron minerals, carbonaceous substances and mica, with an increasing degree of metamorphosis, minerals such as andalusite are increasingly added.
literature
- Walter Maresch, Olaf Medenbach: Steinbach's natural guide. Rocks. P. 252. Mosaik Verlag, Munich 1987, ISBN 3-576-10699-5 .
- Spot slate. Otto Lueger: Lexicon of the entire technology and its auxiliary sciences. Vol. 4, Stuttgart, Leipzig 1906, p. 82.