Chondrites are so-called because they contain chondrules. Chondrules were created when molten droplets of silicates solidified. Then they accreted (form by gradual accumulation or coalescence) in space together with free metals to form the first asteroids 4550 million years ago. Chondrites account for approximately 93% of stony meteorites. They are older than the Earth and the most abundant and complex type of stony meteorite.

Chondrites have different degrees of metamorphism and are thus divided into different petrologic types. They are categorized numerically from 1 to 7 in which 3 is the virtual center. Some scientists only consider numbers from 1 to 6.

Aqueous metamorphism is represented by the numbers 1 and 2, with 1 having obliterated chondrules and 2 containing altered chondrules.

Thermal metamorphism is represented by the numbers 3 to 7, with 3 being unaltered pristine chondrules and 7 being destroyed chondrules. Numbers 4, 5 and 6 are graduations between the two.