What are planetary rings made of?
Planetary rings are made of dust, moonlets, or other orbiting objects. Saturn, Jupiter, Uranus, and Neptune all have ring systems.
Nobody knows exactly. Normally, planetary rings are made up of rocks caused by impacts between planets, moons and asteroids. However, Neptune is not a solid planet, so there is nothing for other space objects to impact on. Also, Neptune's rings are very faint and incredibly difficult to see. Therefore astronomers think the rings of Neptune are made of micrometre dust (dust the size of a millionth of a metre) and ice particles.
The rings of Saturn are a system of planetary rings around the planet Saturn. They consist of countless small particles, ranging in size from microns to meters, each on its own individual orbit about Saturn. The ring particles are made almost entirely of water ice, with some contamination from dust and other chemicals.-- from Wikipedia