Stones 

Slate

Formed millions of years ago, slate has served as important material throughout human history. It has been used in construction and household items.

Slate was originally clay sediments deposited by water. These clay beds lying far beneath the earth's surface were subjected to relatively low temperature and pressure. As a result slates were formed chiefly among older rocks, though more recent slate can be found in regions that experience the folding and compression of mountain-building movement.
The principal minerals in slate are mica, chlorite and quartz.

Slate came into wide use in such items as roofing, flooring, mantels and vanities.