Fukang 44°26′N, 87°38′E
Fukang, Xinjiang Province
Pallasite (main group)
History: An anonymous finder recovered a 1003 kg specimen near Fukang, China, in 2000. The sample was at the Tucson Gem and Mineral Show in February 2005, and seen by D. S. Lauretta of UAz. Approximately 20 kg had been removed from the main mass by the finder before the Tuscon show and the mass investigated at UAz was 983 kg. (D. S. Lauretta, D. Hill, M. Killgore, D. Della-Giustina, Y. Goreva, UAz; I. Franchi, OpenU).
Petrography and Geochemistry: Olivine: Throughout the large mass, olivines vary in shape from rounded to angular; many are fractured. They range in size from <5 mm to several cm. The main pallasite contains several regions of “massive” olivine clusters up to 11 cm in diameter with thin metal veins only a few millimeters in width. Fo86.4 with molar Fe/Mg = 0.1367, Fe/Mn = 40.37, and Ni = 0.03 wt%. Zoning was not observed for Al, Cr, Ca, Mn, or Fe typical of olivines in main-group pallasites. Metal and sulfides: Groundmass is mostly kamacite with some occurrences of kamacite mantles surrounding taenite cores, rounded taenite adjacent to kamacite, and regions of “comb plessite. ” Kamacite contains an average Ni = 6.98 wt%. Schreibersite is enclosed by wide kamacite bands and as mantles adjacent to olivines. Two populations of schreibersite are present with Ni = 26 and 35 wt% near chromite. Vermicular sulfide (troilite) is present in some olivine. Thin veins of kamacite and troilite occur inside many olivines as well. Minor phases: Euhedral chromites up to 0.5 cm, rounded whitlockite adjacent to olivine, and troilite heterogeneously distributed in thin veins. Several regions, ranging from <100 µm to several millimeters, that contain a complex mixture of olivine, low-Ca pyroxene, troilite, and whitlockite were observed adjacent to chromite. Bulk composition: Fe = 89.9 ± 0.3, Ni = 9.0 ± 0.2, P = 0.62 ± 0.02, Co = 0.51 ± 0.01 (all wt%); Ge = 41 ± 4, As = 26 ± 5, Ga = 19.1 ± 0.5, Pd = 5.1 ± 0.2, Au = 2.6 ± 0.2, (all µg/g); Ir = 43 ± 4 ng/g. Oxygen isotopes: δ18O = 2.569, δ17O = 1.179, ∆1 7O = −0.157 (all ‰).
Classification: Pallasite (main group).
Specimens: A total of 31 kg of type specimen is on deposit at UAz. M. Killgore holds a total of 31 kg. An anonymous collector holds the main mass.