Stony Meteorites
Dominated by silicate minerals. This broad family includes primitive chondrites and differentiated achondrites.
- Chondrites
- Achondrites
- Lunar & Martian meteorites
Meteorite Classification Guide
Meteorite classification is a scientific system, not simply a description of colour or shape. Laboratories examine texture, mineral chemistry, metal content, isotopes, and evidence of alteration to connect a specimen with its parent body and history.
This guide introduces the hierarchy collectors encounter most often. Official names and classifications are approved through the Meteoritical Society and published in the Meteoritical Bulletin Database.
Iron Meteorites
Composed mainly of iron-nickel alloys, with structures and trace elements that reveal extremely slow cooling.
- Hexahedrites
- Octahedrites
- Ataxites
Stony-Iron Meteorites
Rare meteorites containing substantial silicate and metallic components, representing complex parent-body environments.
- Pallasites
- Mesosiderites
Primitive material
Chondrites
Ordinary Chondrites
The most common meteorites. Their chemical groups reflect total iron and metal content: H (high iron), L (low iron), and LL (low total iron and low metal).
Carbonaceous Chondrites
Primitive, often volatile-rich meteorites assigned to groups including CI, CM, CO, CV, CK, CR, CH, and CB. Some contain hydrated minerals and organic compounds.
Enstatite Chondrites
Highly reduced meteorites dominated by enstatite. Their main chemical groups are EH and EL.
Other Chondrite Groups
Scientifically distinct groups include R (Rumuruti) and K (Kakangari), along with ungrouped chondrites that do not fit established groups.
Differentiated worlds
Achondrites
HED Clan
Howardites, eucrites, and diogenites share mineralogical and isotopic relationships and are generally linked to asteroid 4 Vesta.
Angrites & Aubrites
Angrites are basaltic, calcium-rich rocks; aubrites are enstatite-rich achondrites formed under reducing conditions.
Ureilites
Carbon-bearing ultramafic achondrites, commonly rich in olivine and pyroxene and often showing impact-related disruption.
Planetary Meteorites
Lunar and Martian meteorites are identified by mineralogy, chemistry, isotopes, and comparison with returned samples or measured planetary atmospheres.
Metallic records
Irons and Stony-Irons
Iron Meteorites
Modern classification relies chiefly on trace-element chemistry and groups such as IAB, IIAB, IIIAB, and others. Structural terms—hexahedrite, octahedrite, and ataxite—describe the metal texture.
Pallasites
Olivine crystals enclosed in iron-nickel metal. Recognized groupings include the main group, Eagle Station group, and pyroxene pallasites.
Mesosiderites
Brecciated mixtures of silicate crustal material and iron-nickel metal, recording large-scale impact mixing on a differentiated parent body.
Ungrouped Material
A meteorite may be scientifically valid yet chemically distinct from established groups. Such specimens can be classified as ungrouped pending further relationships or discoveries.
Reading the numbers
Petrologic Type
| Type | General meaning |
|---|---|
| 1–2 | Strong to moderate aqueous alteration on the parent body; original chondrules may be altered or difficult to recognize. |
| 3 | Least thermally metamorphosed chondritic material; chondrules and primitive textures are well preserved. Decimal subtypes may show finer degrees. |
| 4–6 | Increasing thermal metamorphism and recrystallization, with type 6 showing extensive equilibration. |
| 7 | Very high-grade metamorphism, approaching or showing partial melting; usage depends on classification context. |
History after formation
Shock and Weathering
| Code | What it records |
|---|---|
| S1–S6 | Increasing effects of impact shock in ordinary chondrites, from essentially unshocked material to very strongly shocked material with extensive transformation or melting. |
| W0–W6 | Increasing terrestrial weathering in ordinary chondrites, from no visible oxidation to severe replacement of metal and silicates by alteration products. |
| Fresh fall | A recently recovered fall may preserve glossy fusion crust and relatively unaltered interiors, but freshness is not itself a compositional classification. |
Example
How to Read “NWA 12345 (H5, S2, W1)”
NWA 12345
NWA means Northwest Africa. The number is the approved sequential name, not a quality grade or serial number from a dealer.
H5
H identifies the high-iron ordinary chondrite group. 5 records substantial thermal metamorphism on the parent body.
S2
The specimen is weakly shocked within the ordinary-chondrite shock scale.
W1
The specimen shows minor terrestrial oxidation under the ordinary-chondrite weathering scale.
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