This is a rock.
Rock is solid. This means it is not a liquid like water or a gas like steam. It occurs naturally so it is not man made. There are lots of rocks. They are big. They can also be small. People use them for building. They can be round. Big ones are usually heavy. Small ones are not heavy sometimes. Big rocks are boulders. Tiny smooth ones are pebbles.
These are also rocks: 
