L-Group (Low-Iron)

L Chondrites

Synonyms: olivine-hypersthene chondrites, hypersthene chondrites, Baroti-like chondrites

General: The chondrites of the L group are named for their relatively low content of nickel-iron in its free form - the "L" standing for "low iron". The L group members contain a weight percentage of 20 to 25% total iron, but only 4 to 10% of the nickel-iron is found as free metal. Therefore, the L chondrites are also attracted to a magnet, but much less than their cousins of the H group. Their type specimen is Baroti, a witnessed Indian chondrite fall from 1910.

Description: On the first sight, freshly fallen L chondrites resemble H chondrites, exhibiting dull black fusion crusts, and grey interiors. However, their matrix contains considerably less metal flakes. The L chondrites belong to petrological types 3 - 7, with a characteristic peak at type 6. More than 5,000 have been classified as L6, about 2,000 as L5, just about 600 as L4, and only about 400 as L3. Brecciated members that show clasts of several petrologic types, and other unusual members make up for the rest.

Mineralogy: Besides magnetite and nickel-iron, the L chondrites are composed of olivine and the orthopyroxene hypersthene. Consequently, they have been called "olivine-hypersthene chondrites" or "hypersthene chondrites" in older literature and papers. However, this name is not fitting modern meteoritics, and we would like to discourage the use of these terms.

Origin and Formation: When it comes to the origin of the L chondrites it has been suspected that they might be former parts of the near-Earth asteroid 433 Eros which has been intensely studied by the spacecraft NEAR-Shoemaker, more recently. The reflectance spectra of Eros and the L chondrites seem to match closely - however, most L chondrites show signs of severe shock metamorphism suggesting a violent history of its parent body. Maybe the real parent of the L chondrites was some kind of relative, or even a former part of Eros that has been entirely disrupted when it collided with another asteroid.

Members: With about 8,500 members, including many probable pairings from the hot deserts of Africa and Asia as well as from the ice fields of Antarctica, the chondrites of the L group represent the second largest group of ordinary chondrites. Historic witnessed falls include famous meteorites such as Alfianello, Bovedy, Dubrovnik, and Wold Cottage. More recent but also highly covetted witnessed falls include Barwell, Claxton, La Criolla, Mbale, and Park Forest - just to name a few. Desert finds are abundant, such as SAU 001, a very nice find from Oman, or one of our own finds, Sahara 98222, from North Africa.

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