New England Meteoritical Services

Structural and Chemical Classifications

of Iron Meteorites

The chemical classifications of iron meteorites are identified by Roman numerals and letters. These classifications identify ratios of gallium and germanium to the level of nickel present in the meteorite and form neat groupings when plotted on a graph. One assumption made about chemical classifications is that meteorites in the same chemical group come from the same parent body even though they may differ structurally.

There is also one catch-all chemical group that does not form a neat cluster when graphed. It has been named the Anomalous (ANOM) group.

  • Hexdahedrites - chemical classes IIAB, ANOM
  • Octahedrites
    • Coarsest - chemical classes IIAB, IIIF, ANOM
    • Course - chemical classes IAB, IC, IIE, IIIAB, IIIE, IIIF, ANOM
    • Medium - chemical classes IAB, IID, IIE, IIIAB, IIIF, ANOM
    • Fine - chemical classes IID, IIICD, IIIF, IVA, ANOM
    • Finest - chemical classes IIC, IIICD, ANOM
    • Plessitic - chemical class IIC
  • Ataxites - chemical classes IIICD, ANOM

Coahuila, Mexico. Iron, hexahedrite.


New England Meteoritical Services