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PLNClassification: Diogenite, anomalous W-low / S-low
Time/Place: 2022 in Algeria
Mass: 730g
History: Found in November 2022 in the Ouargla Province in Algeria; later sold to Edwin Thompson in 2023, who subsequently sold the main mass to Paul Stahura.
Physical characteristics: Single stone with minor brown fusion crust. A slice of the interior reveals a moderately vesicular rock.
Petrography: (D. Sheikh, Cascadia) Sample displays a granular texture (triple junctions evident at many grain boundaries) comprised predominantly of slightly-zoned, sub-angular, equant orthopyroxene (~0.9 mm average, largest grain ~ 1.5 mm, ~94 vol.%). Olivine is primarily sub-rounded (~ 0.2 mm average, largest grain ~1 mm) and minorly dispersed throughout the sample (~1 vol. %), although there is an “olivine bundle” identified in the section analyzed that is comprised of numerous olivine grains clustered together that measures 7 mm overall in the longest dimension (~4 vol. %). Other minor phases identified include calcic plagioclase and high-Ca pyroxene (~1 vol. % combined), and accessory phases identified include troilite, chromite, Cr-spinel, and Fe-Ni metal (<1 vol. %). Spherical vesicles are abundant throughout the sample, with the largest measuring ~1.5 cm in diameter.
Geochemistry: Olivine (Fa31.5±1.4, range Fa29.3-33.2, Fe/Mn = 42±1, n=14), Low-Ca Pyroxene (Fs25.5±1.1Wo2.9±1.1, range Fs23.0-27.3Wo0.8-4.0, Fe/Mn = 28±2, n=22), High-Ca Pyroxene (Fs12.2±0.6Wo42.0±1.0, range Fs11.8-12.6Wo41.3-42.7, Fe/Mn = 32±6, n=2), Calcic plagioclase (An85.4±2.5, range An82.2-90.6, n=12).
Classification: Diogenite (anomalous, vesicular, olivine-bearing). The abundant vesicles in this sample are an anomalous feature, similar to that observed in NWA 12973 and Dhofar 700.
CONDITION: slice one side mirror polished other side half polished
