Remember, The present is the key to the past. Rocks are important to our ecomonics because oil and coal are found in rocks. Other rocks are important building products. Limestone is used in road construction, steel-making, concrete and cement. It's an easy way to find the presence of silt, which in some cases is too fine to be felt by hand.
Silt helps identify rocks.
A mineral is a naturally occurring substance with a definite chemical structure. A rock is a naturally occurring combination of minerals cemented together. My favorite rock at the Pound Gap outcrop has a lot of brachiopod fragments. There isn't much coal at Pound Gap.