CV Group
The chondrites of this group are named for their type specimen,
the meteorite of Vigarano, which fell in Italy in 1910. The CV group
has about 50 members, but the number of actual CV falls has to be
estimated to be somewhat lower since many of them are paired finds
from the hot deserts of Africa and the blue-ice fields of Antarctica.
Most CV chondrites belong to petrologic type 3, and only one has
been found to belong to type 2 as well as one other that has been
classified as type 4. The structure and composition of these
carbonaceous chondrites is more close to that of ordinary
chondrites. In a dark-grey matrix of mainly iron-rich olivine, the
meteorites of the CV group exhibit large, well-defined chondrules
that are made of magnesium-rich olivine, often surrounded by iron
sulfide. The meteorites of this group also contain white, irregular
inclusions of different size that often make up more than 5% of the
meteorite. These inclusions are high-temperature minerals called
CAIs (calcium-aluminium inclusions) and are composed of silicates
and oxides of calcium, aluminium, and titanium.
These large CAIs, characteristic of CV chondrites, have been
intensely studied in the famous meteorite of Allende. Allende fell
in Mexico in 1969, shortly before Neil Armstrong took his first step
on the Moon. The CAIs of Allende contain fine-grained, microscopic
diamonds - and those diamonds exhibit strange isotopic signatures
that point to an origin outside of our solar system. They are
interstellar grains that have proven to be older than the earth and
the sun, and probably they are the product of a nearby supernova, of
a dying star that made his last breath when our own system formed.
Traces of this supernova have been trapped within the CAIs and
preserved in the CV group and other carbonaceous chondrites to this
day.
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