What is a chert and how does it form?
Chert is a sedimentary rock composed of pure silica, occurring either in interlayered beds with other sedimentary rocks or as odd-shaped or rounded lumps called nodules found in other sedimentary rocks. The bedded form is often composed of the skeletal remains of tiny marine organisms, and these skeletons can be seen with the aid of a microscope. The nodular chert is formed from the precipitation of quartz from silica-rich ground water, and appears with frequency in limestone.
