Sahara 00177

Sahara 00177 / Ungrouped Carbonaceous Chondrite / Coolidge Grouplet Sahara 00177, Found 2000, Carbonaceous chondrite (C3/4, CV-like, Coolidge-type) A 312 g stone was found by Labenne. Mineralogy and classification (M. Bourot-Denise, MNHNP): related to reduced CVs, similar to Coolidge and Loongana 001. Chondrules, chondrule fragments and CAIs make up ~75 vol% of the meteorite. Overall, chondrules are smaller than in Allende, with a mean size ~500 µm. CAIs (~10 vol%) are large, up to 1 mm in size. The largest and most abundant chondrules are type-I, porphyrytic olivine-pyroxene chondrules, often of irregular shape, with olivine crystals in the 10–40 µm size range, and abundant opaque beads. Type specimen, 4 g, MNHNP, main mass with Labenne. Sahara 00177, Found 2000, Carbonaceous chondrite (C3/4, CV-like) A 312 g stone was found by Labenne. Mineralogy and classification (M. Bourot-Denise, MNHNP): related to reduced CVs, similar to Coolidge and Loongana 001. Chondrules, chondrule fragments and CAIs make up ~75 vol% of the meteorite. Overall, chondrules are smaller than in Allende, with a mean size ~500 µm. CAIs (~10 vol%) are large, up to 1 mm in size. The largest and most abundant chondrules are type-I, porphyrytic olivine-pyroxene chondrules, often of irregular shape, with olivine crystals in the 10–40 µm size range, and abundant opaque beads. Less abundant metal-poor barred olivine, radial pyroxene and other chondrules are generally smaller (100–300 µm) and more rounded. Olivine, Fa8.0 ± 1.0 (range: 5.0–9.6); low-Ca pyroxene Fs7.6 ± 2.4 (range: 3.4–10.5). Chondrule mesostasis is completely devitrified. A few chondrules are partially rimmed with silica (as is the case in Coolidge). Fe-Ni metal is kamacite, with minor taenite. Weakly shocked, metal is not warped, troilite is monocrystalline. Moderately weathered; metal grains, especially those in the matrix or on chondrules edges, have a 2–5 µm-wide limonite rims; veins in chondrules silicates are also filled with limonite; troilite is unaltered. Type specimen, 4 g, MNHNP, main mass with Labenne. Groups and grouplets: Amoung classifying scientists it’s an unwritten law in the naming of new meteorite groups that it needs at least five members to constitute a new group. However, certain new groups and grouplets have been proposed in the past, although they don’t have the necessary number of established members. This is done to show obvious relations between these ungrouped meteorites, and these grouplets often are the precursors of new groups to be formed in the future. The Coolidge grouplet, named for the meteorite of Coolidge that was found in Kansas, USA, in 1937, is a good example for such a “group in progress”. Together with our own desert find, Sahara 00177, there are at least three other carbonaceous chondrites – officially designated as C UNGR – that show a similar high matrix to chondrule ratio as Coolidge as well as the same enrichment in refractory elements. Maybe this grouplet will gain the status of a fully accepted group as soon as new members are found and recognized in the wealth of new meteorite finds from the hot deserts of Africa and Asia, as well as from the blue-ice fields of Antarctica.