Pure limestones are white or almost white, but impurities, such as clay, sand, organic remains, iron oxide, and other materials, cause them to exhibit different colors, especially on weathered ...

"However, clay content is only one piece of the puzzle ... future to estimate the physical properties of fine-grained ...

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.

The basalt which makes up the Giant’s causeway is an igneous rock. Sedimentary rocks are formed by small rock pieces which are transported by rivers and laid down in layers. Chalk is a ...