knotenschiefer การใช้

• Like fleckschiefer, fruchtschiefer and garbenschiefer, knotenschiefer is a variety of contact metamorphic slate.
• Fruchtschiefer occurs at 500 癈 . Knotenschiefer is characterised by small nodules, up to one centimetre in size, and nodular deposits of mica as a result of the growth in grain size during metamorphism.