Acapulcoites are rare achondrite meteorites (= meteorites that lack rounded structures called chondrules).  About 64 acapulcoites have been documented.  They have a finely-crystalline texture and are composed of a mix of mafic silicate minerals (olivine, pyroxenes, plagioclase feldspar) and metallic iron-nickel.


The overall chemistry of acapulcoites is generally the same overall chemistry seen in ordinary chondrites.  This suggests that acapulcoites are the result of metamorphic heating of chondrite material, involving solid-state recrystallization but generally no significant loss or gain of component elements.  Such rocks have been called metachondrites (metamorphosed chondrites).


The sample shown below is the NWA 2989 Meteorite, found in northwestern Africa in 2005.  It is reportedly paired with several other acapulcoites discovered in the same general area (the list includes at least the following: NWA 2656, NWA 2699, NWA 2714, NWA 2866, and NWA 2871).


The specific parent body in the asteroid belt from which acapulcoites are derived is unknown.  What is known is that another group of rare achondrite meteorites, the lodranites, come from the same body.


Published age information on acapulcoites shows that the parent body is 4.555 to 4.562 billion years old.  Most acapulcoites & lodranites have cosmic-ray exposure dates of 4 to 7 million years, indicating when these rocks were ejected from the parent body.


Acapulcoite slice (above & below; 1.3 cm across at its widest) showing microcrystalline texture and mixture of mafic silicate minerals & iron-nickel metal.  The Fe-Ni metal shows up black in the photo above & bright silver in the photo below.  Note the thin veins of metal running through the rock.  This is characteristic of acapulcoites.




(More info. on NWA 2989, which = NWA 2656)



Info. mostly synthesized from Hutchinson (2004 - Meteorites, a Petrologic, Chemical and Isotopic Synthesis) and Touboul et al. (2007 - 38th Lunar and Planetary Science Conference Abstracts # 2317).  Some info. from James Wittke & John Kashuba & David Weir.



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