Sedimentary rocks close sedimentary rockSedimentary rocks ... which originates from clay. Slate is dark grey/green in colour and can be split into thin layers for use as roofing material.

Shale is a sedimentary rock made up of tiny grains of silica, clay and other minerals. Many types of rock have few physical ...

Thousands of enigmatic hills and mounds dotting the northern plains of Mars may hold the key to understanding the planet’s ...