1) Sedimentary rock 
Tonstein (from the German `Ton`, meaning clay, plus `Stein`, meaning rock) is a hard, compact sedimentary rock that is composed mainly of kaolinite or, less commonly, other clay minerals such as montmorillonite and illite. The clays often are cemented by iron oxide minerals, carbonaceous matter, or chlorite. Tonsteins form from volcanic ash de...