D’Orbigny Angrite

Buenos Aires Province, Argentina
Single 16.55 kg piece

Found 1979
Recognized as a meteorite 1998
Classified as an angrite 2000

Angrites have been considered to be basaltic rock.  Research on the d’Orbigny meteorite is providing evidence that it was not formed through conventional igneous processes on a differentiated asteroid.  Some workers suggest a rare condensation process in the early solar nebula.  The main constituents are anorthite and zoned olivine and augite.

This thin section has a vesicle that, in basalt, would have been formed by gas.  In d’Orbigny they are thought to be voids vacated by earlier spheres of solid matter.  Glass occurs in some of these spaces and also between mineral grains and in some olivine crystals.  Thin section maximum diagonal dimension is 26 mm.