O meteorito Pontes e Lacerda foi encontrado por um garimpeiro chamado M. Braga, enquanto estava procurando ouro com um detector de metal. O mesmo enviou amostras para Andre Moutinho, que realizou testes preliminares e confirmou a origem meteoritica do material. Amostras foram então enviadas a Dra Zucolotto para uma completa análise e classificação.
From Meteorite Bulletin entry:
History: The meteorite was found by a prospector, Mr. M. Braga, while he was searching for gold with a metal detector. The finder sent samples to Andre Moutinho who performed preliminary tests that confirmed the samples have a meteoritic origin. Samples were then provided to Dr. Zucolotto for a complete analysis and classification.
Physical characteristics: A regular weathered round mass weighing 224 g and measuring about 49 × 33 × 3 1 mm
Petrography: (M. E. Zucolotto, Rio) The examined slice is a 9 cm2 endpiece with no fusion crust and heat affected zone. It shows exfoliation along corroded Widmanstätten planes, typical of long terrestrial exposure. Etched sections display a normal, medium Widmanstätten structure with kamacite bandwidth of 1.05±0.15 mm; some subboundaries are decorated with tiny rhabdites. In a heavy etching, the kamacite shows an abundant cross-hatched pattern. Taenite and plessite are common (visually ~60% by area) as comb and net plessite and as martensitic and black etching with duplex fields. Neumann bands weakly developed. Schreibersite (to 500 μm) present in the interiors and borders of kamacite bands. Rhabdites are very common as 1-5 μm thick prisms. No troilite was observed in the examined section, although two holes are present as a lost inclusion
Geochemistry: (J. T. Wasson UCLA) INAA, 8.1 wt% Ni; 0.49 wt% Co; 103 ppm Cr; 181 ppm Cu; 20.8 ppm Ga; 5.43 ppm As; 4.84 ppm Ir; 0.738 ppm Au. Composition of major phases (A. Tosi, IGEO-UFRJ) kamacite (Ni 7.2±0.2 %, Co 0.65±0.15%, P 0.02%).
Classification: (J. T. Wasson, UCLA) This meteorite can be compared to other IIIAB iron having Au in the range 0.686 to 0.770 ppm. No similar IIIAB has been found in South America. The only one that has a similar composition is Hot Springs, but even it is resolvable in terms of As and probably also Au.
Specimens: Main mass with Andre Moutinho, 22 g Rio