CM2 meteorites are regolith breccias. They’ve been through cycles of crushing and lithification at an asteroid surface. They are dark with opaque matrix and varying amounts of chondrules, olivine aggregates, CAI and mineral grains.
This is a sample of a CM2 fall that is reported to have distinct lithologies. Our samples, whose early field name was Jaipur, are dark and brecciation is extensive. In some, chondrules, mineral grains and olivine aggregates are sparse. We have found clasts with fine grained dust mantles.
27 × 46 mm petrographic slide. Early field name was Jaipur, the name of a city about 14 km from the fall site. Incident light.
Brecciated and comminuted material. Two clasts on left are mantled with fine dust. The upper one is an olivine aggregate. Its dust texture hints at accretionary layering. Third photo field of view is a half millimeter wide. Incident light.
In center is an olivine aggregate. FOV=3.1 mm wide. Incident light then cross-polarized light.
From a second slide, toward the left are two dust mantled aggregates and at the right a bright white CAI. FOV=3.1 mm wide. Incident light then cross-polarized light.
Also in the second slide is this light colored clast. Above it is a porphyritic chondrule. FOV=3.1 mm wide. Incident light then cross-polarized light.
From a third slide, a large mass of fine olivine, chondrule fragments and, on the left a bright orange barred olivine chondrule. FOV=3.1 mm wide. Cross-polarized light.