Fairburn        43.603°N, 103.026° W

Custer County, South Dakota, USA

Found: 1907

Classification: Iron meteorite (IAB, ungrouped)

History: Found in 1907 by Otis Roberts in a railroad car transporting gravel for ballast quarried from terrace deposits of Pleistocene age on the west side of the Cheyenne River in Custer County, southeast of Rapid City, South Dakota (Ziegler, 1914, p. 54-58). The original 445 g mass described by Victor Ziegler was in the collection of the South Dakota School of Mines. In 1982 a 56 g portion was purchased by James M. DuPont, on which studies were conducted from 2004 to 2012.

Physical characteristics: A smooth, rounded ovoid silvery mass (445 g) with thin weathering patina and a specific gravity of 7.306.

Petrography: (G. Jerman, MSFC) The specimen is composed mostly of kamacite with some taenite and plessite. Some globular and ribbon-like schreibersite is present, but no silicates, sulfides or carbides were found. Kamacite bandwidth 1.34 mm (range 0.37-1.96, n=18).

Geochemistry: Trace elements (G. Chen and C. Herd, UAb) Analysis of a 3.1 g portion by ICP-MS using North Chile as internal standard gave: Ni=78.8, Co=5.3 (both mg/g); Cr=17, Cu=132, Ga=76.5, Ge=255, As=6.1, Ir=2.3; Pt=5.2, Au=1.49 (all μg/g), Sb=420, Re=220 (both ng/g).

Classification: Iron meteorite (IAB, ungrouped). Chemical data comparisons for possible matches to regional and other common irons were inconclusive.

Specimens: A total of 52 g is on deposit as part of the DuPont Collection owned by PSF.