Achondrite

An achondrite is a stony meteorite that consists of material similar to terrestrial basalts or plutonic rocks. Compared to the chondrites, they have all been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies. As a result, achondrites have distinct textures and mineralogies indicative of igneous processes.

Achondrites account for about 8% of meteorites overall, and the majority (about two thirds) of them are HED meteorites, originating from the crust of asteroid 4 Vesta. Other types include Martian, Lunar, and several types thought to originate from other as-yet unidentified asteroids. These groups have been determined on the basis of e.g. the Fe/Mn chemical ratio and the ¹⁷O/¹⁸O oxygen isotope ratios, thought to be characteristic "fingerprints" for each parent body.

Achondrites are classified into the following groups:
* Primitive achondrites (PAC group)
** Acapulcoites
** Lodranites
** Brachinites
** Winonaites
** Ureilites
* Asteroidal achondrites (evolved achondrites)
** HED (Vesta) meteorites
*** Howardites
*** Eucrites
*** Diogenites
*** "Dunite diogenite"
*** "Olivine diogenites"
** Angrites
** Aubrites
* Lunar meteorites (Lunanites)
** Impact breccias
** Lunar Basalts
* Martian meteorites (SNC)
** Shergottites
** Nakhlites
** Chassignites
** OPX martian meteorites (ALH 84001)