Tektites are an Impactite, natural glass formed when a meteorite, asteroid, or comet impacts Earth. They are usually pitted or grooved (or both) and are usually not smooth. They are made up of melted terrestrial (Earth) rock. Although the composition may vary they are mostly made of silica glass with inclusions of magnesium, iron and other elements. Tektites come from the Earth, whereas meteorites come from space. The name Tektite comes from the Greek, meaning "molten".