Everyday Uses of Rocks and Minerals - Shelf 1
Gypsum is ubiquitous in our lives as the basis for drywall. It contains water in its mineral structure, which it loses when heated, providing an initial line of defense against building fires.
In the time before dry-erase boards, all education relied upon chalkboards made from slate, which is clay that has been cooked by heat and pressure deep within the earth. Chalk is a limestone made of the skeletons of millions of microbes that once lived at the bottom of the sea , so it's really a fossil.