Aubrites

Aubrites are enstatite achondrites from a parent body that differentiated under highly reducing conditions, the same unusual chemistry that produced enstatite chondrites. Pale, almost white, and dominated by nearly iron-free enstatite, aubrites are visually distinctive and scientifically unusual. Unless specifically stated in the listing, specimens in this collection are Meteoritical Bulletin classified.

From a reducing environment

Most meteorites formed under oxidizing to mildly reducing conditions. Aubrites formed under the most reducing conditions of any differentiated meteorite group, an environment so oxygen-poor that iron remained in metallic form rather than entering silicate minerals. The result is enstatite (MgSiO₃) that is almost completely free of iron, giving aubrites their distinctive pale gray to white color.

Most aubrites are brecciated, having been disrupted by impacts on their parent body. Fresh surfaces show a light gray, granular texture dominated by coarse enstatite crystals. The unusual mineralogy includes sulfide minerals: oldhamite (CaS), niningerite (MgS), and alabandite (MnS), that are essentially unique to the reduced enstatite meteorite groups.

Frequently asked questions

Why are aubrites white or pale? Because their enstatite is nearly iron-free. In most silicate minerals, iron substitution causes dark coloration. Enstatite that formed under highly reducing conditions contains almost no iron, resulting in a pale mineral and a light-colored meteorite.

Are these specimens authenticated? Unless specifically stated in the listing title or description, specimens in this collection are Meteoritical Bulletin classified with a direct link to the official record. Every purchase ships with a Treasure Coast Meteorite Co. certificate of authenticity.

See also: Angrites · Ungrouped Achondrites · What Is an Achondrite?