CO Carbonaceous chondrites
are named for the Ornans meteorite that fell in France in 1868. They
some similarities in composition and chemistry to the CV chondrites and
may have formed with them in the same region of the early solar system.
As in the CV group, CAIs are present but are commonly much smaller and
spread more sparsely in the matrix. Also typical of COs are small
inclusions of free metal, mostly nickel-iron, that appear as tiny flakes on the polished surfaces of fresh, unweathered samples.
All CO meteorites are of the
petrologic grade type 3 with only about 30% of
the meteorite being composed of large chondrules.