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Carbonaceous Chondrites - CR Group

 
CR Group Type Specimen Renazzo - 0.736g Slice

The CR Type Specimen: Renazzo

(a thinly cut 0.736g partial slice)

Peter Marmet


A 1.78g Slice of CR2 Chondrite NWA 530

Slice of CR2 Chondrite NWA 530

(a typical 1.78g partial slice)


An 18.24g Endcut of CR2 Chondrite NWA 801

The CR2 Chondrite NWA 801

(a large 18.24g endcut of this most abundant of all CR members)

 

Synonyms: Renazzo-like carbonaceous chondrites

General: The chondrites of the CR group are named for their type specimen Renazzo, a meteorite that fell in Italy in 1824. The CR chondrites are closely related to two other metal-rich groups, the CH and CB chondrites, and together they form the CR clan.

Description: The CR chondrites contain abundant free metal in the form of nickel-iron and iron sulfide of up to 10%. This metal is found in the black matrix as well as in the large and clearly visible chondrules that make up about 50% of the meteorites. The chondrules are well defined, and most CRs belong to petrologic type 2.

Mineralogy: Like the members of the CM group, the CR chondrites were subjected to the process of aqueous alteration. They also contain hydrosilicates, traces of water, and magnetite. Reduced nickel-iron metal, and iron sulfides are found in the black matrix as well as in the chondrules.

Origin & Formation: Scientists have searched for the parent body of the CR chondrites, comparing different reflectance spectra of asteroids with the spectra of CR members. There is a good match between the spectra of the CRs and one of the most prominent asteroids in our solar system, 2 Pallas, the second largest asteroid known. It's not clear if the other members of the CR clan, the CB and CH chondrites, share the same parent body; it's much more probable that their parent bodies formed in the same region of the early solar nebula.

Members: If we exclude all probable pairings from NWA and the ice fields of Antarctica, there are only about 28 different CR chondrites known. The most prominent members are the only two witnessed falls, Al Rais and Renazzo, but also the less prominent desert finds are highly coveted among collectors, such as DaG 574, El Djouf 001, or the more common NWA 801.

 

Classification of Meteorites

> A New Classification Scheme
> Primitive Meteorites
> Differentiated Meteorites
> Classification Index

Chondrite Clans & Classes

> Carbonaceous Chondrites
   > CI Group  (Ivuna-like)
   > CM Group (Mighei-like)
   > CV Group (Vigarano-like)
   > CK Group (Karoonda-like)
   > CO Group (Ornans-like)
   > CR Group (Renazzo-like)
   > CH Group (High-Iron-type)
   > CB Group (Bencubbin-like)
   > Metamorphosed CCs
   > Ungrouped CCs
> Ordinary Chondrites
   > H Group  (High-Iron)
   > L Group  (Low-Iron)
   > LL Group (Low-Iron, -Metal)
   > Transitional OCs
> Other Chondrites
   > E Group (Enstatite)
   > R Group (Rumurutiites)
   > K Group (Kakangariites)
   > F Group (Forsterite)
   > Ungrouped Chondrites
> Metachondrites & PACs
   > Acapulcoites
   > Lodranites
   > Ureilites
   > Winonaites
   > Other Metachondrites

Achondrite Clans & Classes
Siderite Clans & Classes

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