Porto Alegre        30°01’59"S, 51°13’48"W

Rio Grande do Sul, Brazil

Found: 2005

Classification: Iron meteorite (IIIE)

History: A single mass weighing about 200 kg was found in the city of Porto Alegre. The finder, the date and the exact location are not known, but the discovery was made prior to 2005 based on a letter from Dr. Hardy Grunewaldt, who noted the meteorite during a visit to the Museum of Catholic University of Porto Alegre. The current owner of the meteorite, Dr. Jeter Bertoletti, is the former director of the museum.

Physical characteristics: Severely weathered with no signs of the original shape and dimensions caused by mass loss from exfoliation. In samples examined at MNRJ, the corrosion has progressed so far that various fragments failed to disclose any unweathered material. Corrosion penetrates to the very center, particularly along octahedral planes, which make lamellar width measurements difficult.

Petrography: (M.E.Zucolotto, MNRJ) Etched preserved sections display a coarse Widmanstätten structure of swollen, short kamacite lamellae with an average width of 1.6 ± 0.3 mm. A wide zone of kamacite adjacent to taenite-plessite and phosphides are altered to oxides. The interior of some plessite fields are severely corroded showing a contrast between dark corroded alpha phase and bright preserved gamma phase. Weathering selectively attacks the nickel and phosphorous-depleted ferrite adjacent to the rhabdite precipitates that are very abundant in some kamacite lamellae. Taenite and plessite cover about 20-25% by area mostly as acicular, comb and dense martensitic fields.

Geochemistry: (J.T. Wasson, UCLA) Bulk composition (INAA): Ni = 90.2, Co =4.96 (both mg/g); Cu = 146, Ga = 18.2, As = 5.65, Ru = 8.7, W = 0.80, Ir = 0.148, Pt = 6.1, Au = 0.898, Cr = 71 (all ppm).

Classification: Iron, coarse octahedrite (IIIE), very weathered.

Specimens: A 20 g sample plus one polished thin section are on deposit at MNRJ. The main mass is with Dr. Jeter Bertoletti in Porto Alegre.