Asteroid Belt

The asteroid belt is a 'belt' of rocky bodies between Mars and Jupiter that is centered around 2.7AU. The total mass of the Main Asteroid Belt may be less than 1/1000 of the mass of Earth. If all the asteroids were combined together, their diameter would be about 1,300-1,500 kilometers across, less than 1/2 the diameter of the Moon.

Most asteroids in the Main Belt are composed of three materials. 92.9% are composed of silicates (stone), 5.7% metals (mainly iron and nickel) and the rest as a mix of those materials and carbon-rich substances.
The largest asteroid in the main asteroid belt is Ceres.