Posted on Leave a comment

Classification Punctuation for Chondrites

The Meteoritical Bulletin is filled with incredible meteorite-related information. However, even the most experienced collector might be puzzled when evaluating a classification and trying to understand the various punctuation used by the Nomenclature Committee. For example, do you understand the difference between an L/LL3 and an L(LL3)? Please note that the punctuation only covers chondrites. There is little carryover into the achondrites, irons and stony-irons, and even within these other groups, one can find discrepancies.

Meaning Behind Punctuation in Chondrite Classifications:

G = chondrite group (H, L, LL, CM, CK, R, …)
Gx = first chondrite group
Gy = second chondrite group
Ta = first chondrite petrologic type
Tb = second chondrite petrologic type

  • Parentheses
    • Gx(Gy) means a chondrite either of Group X or less likely Group Y. Example: L(LL3)
  • Slash
    • Gx/Gy means a chondrite of either Group X or Group Y. Example: L/LL3
    • One exception is Isheyevo, CH/CBb, where the slash means a chondrite that is transitional between the CH group and the CB group.
  • Dash
    • GxTa-Tb means a chondrite comprised of a breccia whose clasts/components range from petrologic Type A to Type B. Example: CK3-6
    • If A and B are one level apart, then means a chondrite of Type A and Type B. Example: R3-4
    • If the dash comes at the end of the group or type, then what follows provides added information. Examples: -melt breccia, -an, -ung
  • Period
    • Used to denote a chondrite’s petrological subtype and only associated with Type 3 (unequilibrated), Type 2 and presumably Type 1. Example: CO3.0
Leave a Reply