What is a meteorite in geology ?

Meteorite : definition

Meteorites are rocky or metallic fragments coming from interplanetary space and reaching Earth. The majority come from the asteroid belt that gravitates between Mars and Jupiter. Meteorites are classified according to their composition into three categories :

- Stony meteorites, subdivided into chondrites, composed of metal grains and chondrules (small spherules, consisting mainly of orthopyroxenes, olivine and rare plagioclases), and achondrite, rocks close to pyroxenites and dunites, made up of pyroxenes and olivine, with rare metals.

- Lithosiderites, or siderolites, containing silicates (olivine, pyroxene, anorthite) and metals (iron and nickel) in equivalent proportions.

- Siderites, or irons, essentially made of metals (iron, nickel and iron-nickel alloys).

Meteorites are the oldest materials in the solar system and provide information on the internal composition of the planets, hence their major interest in geology and planetology.

The largest known reach 60 tons ; their impact creates a shock metamorphism, local but very violent, generating breccia (impactites), and a crater (astrobleme).