Carbonaceous Chondrites - CV Group

Synonyms: Vigarano-like carbonaceous chondrites

General: The CV chondrites are named for their type specimen, Vigarano, a meteorite that fell in Italy in 1910. However, the most famous CV member is without a doubt Allende, a meteorite that fell in a large shower in Mexico in 1969.

Description: CV chondrites are dark-grey rocks, more dense and less porous than the CI or CM chondrites. In fact, their structure and composition is more close to that of ordinary chondrites, and most of them belong to petrologic type 3. CV chondrites usually exhibit a 60:40 proportion of chondrules to matrix, and the chondrules are mostly large, and well defined. Typically, the CVs also exhibit large CAIs (calcium-aluminium-inclusions).

Mineralogy: The matrix of the CVs consists mainly of Fe-rich olivine, while the chondrules are made of Mg- rich olivine, often surrounded by iron sulfide. The CAIs – white, irregular inclusions of different size that often make up more than 5% of the meteorite – are high- temperature minerals, composed of silicates and oxides of calcium, aluminium, and titanium.

Origin & Formation: Those CAIs have been intensely studied in the famous Allende meteorite. They contain fine-grained, microscopic diamonds and those diamonds exhibit odd isotopic signatures that point to an origin outside of our own solar system. These nano-diamonds are interstellar grains that are older than the Earth and the Sun, and they are probably 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 up to this day. The actual parent body of the CV group is yet unknown, but the reflectance spectra point to K-type asteroids as a possible source of these meteorites.

Members: The CV group has about 70 members, but the number of actual CV falls has to be estimated to be somewhat lower since many of the CV samples in our collections are more or less obviously paired finds from the hot deserts of Africa, and the blue-ice fields of Antarctica. Famous historic CV3 falls include Allende, Bali, Grosnaja, Kaba, and the CV namesake, Vigarano.