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.
