When the Apollo moon landings were conducted, astronauts brought rock samples back to Earth. These samples consisted of a variety of moon rocks and meteors that had impacted over millennia. When a meteor strikes a solid body, heat and shock are by-products of the impact. The moon contains silica particles that can be turned into glass. There are very small amounts of glass scattered across the moon due to meteor impacts. Astronauts found glass pieces, especially in the breccias areas where meteor strikes had occurred. While they could not bring back every piece of rock or glass found, the astronauts did collect hundreds of pounds of rock as well as small pieces of lunar glass.