They are usually covered with a white rock dust, usually powdered limestone, which settles coal dust. Nature's rust, Goethite, formed by weathering iron-bearing rocks, was sought by Native Indians for face paint. The ancient Romans used pumice mixed with lime as a cementing material. The Egyptian pyramids are made from limestone. Some animals use simple rocks to help them get at their food.
Otters use rocks to break open clam shells.
Some birds fly over eggs, dropping stones to break them open. Australian aborigine people used quartz in a magical ceremony to make rain fall. Inc. All Rights Reserved.