A chondrite is a stony (non-metallic) meteorite that does not show signs of overall melting. They typically include round grains (chondrules) which are interpreted as rapidly melted and cooled aggregates of cosmic dust and assumed to be material formed very early in the life of the solar system. There is not a consensus on the details of their formation, i.e., what could cause the required heating and cooling. Theories:
The term achondrite refers to such meteorites that do not include chondrules, generally presumed to have formed at a later time.