existed before the Earth was formed. Presolar grain (and, less frequently, "stardust" or "presolar stardust") is the scientific term referring to refractory dust grains that condensed from cooling ejected gases from individual presolar stars and incorporated into the cloud from which the Solar System condensed.

Many different types of presolar grains have been identified by laboratory measurements of the highly unusual isotopic composition of the chemical elements that comprise each presolar grain. These refractory mineral grains may