Amoeboid Olivine Aggregate

AOA in NWA 3118 using partially crossed-polarized light to see through the glassy melt. FOV=1.9mm. Image Credit: John Kashuba

Millimeter sized, fine-grained inclusions present to a few volume-percent in most carbonaceous chondrites. They can be round but can also be irregularly shaped like an amoeba (thus the name amoeboid). They are forsterite (Mg-rich olivine) and Ca-Al-Ti mineral aggregates. The most characteristic texture of AOAs is an anorthite core (sometimes associated with spinel and augite) rimmed by Al-diopside which overgrows olivine. AOAs were first described in the heavily altered Allende CV3 meteorite.

To see more images and get a more in-depth definition, please refer to the Nov 1, 2015 article in Meteorite Times by John Kashuba.

Some or all content above used with permission from J. H. Wittke.

This entry was posted in . Bookmark the permalink.