Click here to view the "Meteorite Article Archive. HED group meteorites Part 2, diogenites NWA 5597, a diogenite achondrite with a total known weight (TKW) of 232.60 g. Two stones were found near the village of Outat el Hadj in Morocco by Mr. Abdessmad in 2007. One more stone was found in 2008. The meteorites show a fresh sandblasted or desert etched crust with remnant flow lines on the 52g individual. The image above shows the 119g stone Image above shows the 52g stone of NWA 5597. Diogenites are igneous rocks derived from the mantle of a common parent body with eucrites and howardites. Together these achondrites form the HED group. Asteroid 4 Vesta has been proposed as the parent body for these basaltic achondrite meteorites. Diogenites consist mainly of coarse grained magnesium-rich orthopyroxene with accessory chromite, troilite and Ni-poor metal. Few contain smaller amounts of olivine and plagioclase. Unlike the other members of the HED group diogenites are of remarkably uniform major element composition. Image above shows a close up of the 119g stone. As can be seen the pyroxene in diogenites is often in the form of sizeable crystals. Both individuals of this find show large (>11mm) orthopyroxenes indicating slow cooling in a magma chamber in considerable depth below the surface of the parent body. Both meteorites display a patchwork of glossy crust on a greenish honeycolored lithology typical for slightly weathered diogenites in the field. Fusion crusts of diogenites tend to be more sensitive to mechanical abrasion than those of ordinary chondrites 19.5g endcut taken from the 52g Outat el Hadj diogenite displaying large orthopyroxenes. Pictured above is a 58.01g individual of the Bilanga meteorite. Bilanga is a unique magnesium-rich and calcium-poor diogenitic breccia and one of only 11 witnessed falls of a digenite meteorite. Large orthopyroxe crytals are visible in the bright greenish matrix. The Image above shows a 72g fragment of the very rare Ca-poor diogenite Tatahouine. This collection specimen represents a witnessed fall from June 1931 in Tunesia. Tatahouine exploded at the end of the cold flight into a cloud of fragments with only a handful of pieces exceeding 30 grams in weight. This golfball sized specimen has still Tunesian soil adherent. The meteorite shows exceptionally large orthopyroxene crystals. 43.20g endcut of NWA 4473, a diogenite with unknown find location that was purchased at Lâayoune, Morocco, in July 2006. This extraordinary diogenite was originally thought to be of lunar orgin due to its bright yellowish green angular clasts which are typical for lunar surface breccias. However the analysis turned out that the meteorite is actually a brecciated diogenite. NWA 4473 shows the same obvious lithology as the diogenitic breccia NWA 4808 which was purchased in Erfoud in 2006 by S. Ralew and might be paired. Fractured surface of NWA 4473 that clearly shows the bright clastic brecciation untypical for diogenites. NMR scalecube is 1 cm Diogenite from the find location of NWA 5480. Compact angular mass shaped like a short hammer head. Thick wind polished fusion crust intersected by a coarse pattern of contraction cracks covers two thirds of the meteorite. Due to their higher melting point sizeable chromite aggregates withstood the melting and ablation of the surrounding material and now protrude from the fusion crust. The matrix of the meteorite is of a striking green color and appears visually very similar to the Tatahouine diogenite. On the crust free portions large pyroxene crystals are visible. This meteorite was found together with at least four other stones in 2009 near Agaraktem at the border of Mali and Mauretania in the westernmost part of the Erg Chech. The specimens are awaiting publictaion under a seperate NWA number. Return to the "Meteorite Article Archive".     © 2001-2011 NigerMeteoriteRecon