Northwest Africa 6685 (NWA 6685)
Classification: Primitive achondrite (Lodranite)
History: Purchased by Giorgio Tomelleri from a dealer in Erfoud, Morocco.
Physical characteristics: A complete stone weighing 524 g, with fusion crust.
Petrography: (V. Moggi Cecchi, G. Pratesi, S. Caporali MSP). The thin section is dominated by large olivine and subordinate orthopyroxene phenocrysts (to 8 mm) embedded in an interstitial fine-grained matrix of the same phases. The matrix grains range from 0.01 to 0.1 mm. Plagioclase is absent. Opaques consist of kamacite and troilite, frequently altered to iron oxides.
Geochemistry: Orthopyroxene, Fs10.7, Fe/Mn=14; olivine, Fa10.8, Fe/Mn=23; Ca-pyroxene, Fs3.4En52Wo44.6; Cr in troilite=0.60 wt%; Oxygen isotopes (I.Franchi, R.Greenwood, OU): δ17O = 0.10; δ18O = 2.50; Δ17O = -1.2 per mil.
Classification: Achondrite (lodranite). Highly weathered. Moderately shock.
Specimens: 23.4 g is on deposit at MSP (MSP 5151).