this is why i love this forum we all want to know more about the same thing a think tank for razors and rocks. i found alot of info on wikipedia look up shale and look up slate they are both made of all most the same material i think its through the end process that make the stones different ,compaction,heat ect. ok just found this from wikipedia "Shales that are subject to heat and pressure of metamorphism alter into a hard, fissile, metamorphic rock known as slate. With continued increase in metamorphic grade the sequence is phyllite, then schist and finally to gneiss." ok same stuff but the end process makes it into a different preforming rock. like translucent ark and a cf . we did get off track with the true question what is a thuringian made of i think its some sort of fossilized clay with different minerals in it i dont think it has shale in it but i could be wrong the quest continues.