Berduc                                                            Centroid  31º54.6’N, 58º19.7’W

Colonia Berduc, Argentina

Fall: 7 April 2008, 01h02m28s GMT (UTC)

Ordinary chondrite (L6)

History: A bright bolide of absolute magnitude -16±2 was widely seen over Argentina and Uruguay. The fireball was recorded by U.S. satellite visible-light sensors as reported by Douglas O. ReVelle (Los Alamos National Laboratory). A crude analysis of recorded infrasound data suggests a 0.01 kT event as analyzed by Peter Brown and Wayne Edwards (University of Western Ontario, Canada). The event occurred nearby the Argentina-Uruguay border. Eyewitnesses, interviewed by members of AEA and Gonzalo Tancredi (DAFC), reported that the fireball traveled from west to east and experienced several fragmentations along its trajectory causing audible detonations that shattered buildings in the area of fall. Several stones were found by members of Asociación Astronómica Entre Ríos a few days after the fall in the countryside around Colonia Berduc. The largest piece is a 154-g sample located in MNCNA-AS that acts as the hosting institution. The MLEDU museum has a 95-g piece, and CASLEO has a piece of 21 g. The rest of the mass remaining in Argentina is in private collections.
Physical characteristics: The known stones exhibit a fresh black fusion crust; total recovered mass remaining in Argentina ≈ 737 g. Other pieces were collected or bought by dealers and sold in the U.S., so the total mass was probably higher. To avoid Argentina regulations we know that some pieces have been sold under the name “Arroyo Malo”. Several expeditions leaded by Gonzalo Tancredi and Leda Sanchez (DAFC) to that region ruled out the possibility that these pieces were found in that locality of the nearby Uruguay.
Petrography and mineral compositions: (Alan Rubin, UCLA; Jordi Llorca, UPC; Josep M. Trigo-Rodríguez, CSIC-IEEC) Olivine (Fa 23.7±0.5; n=23), low-Ca pyroxene (Fs20.3±0.5 Wo1.4±0.2; n=25) and kamacite (7.1±0.8 mg/g Co; n=7). Berduc contains 8.1 wt.% metallic Fe-Ni.
Classification: The modal abundance of metallic Fe-Ni and the mean olivine, low-Ca pyroxene and kamacite compositions of Berduc indicate that the rock is an L-group chondrite. Berduc is highly recrystallized and contains poorly defined radial pyroxene (RP), porphyritic olivine (PO), porphyritic olivine-pyroxene (POP), and barred olivine (BO) chondrules that are well integrated into the matrix.  Plagioclase grains typically exceed 50 µm in size, indicating that the rock is petrologic type 6. This is consistent with the relative compositional homogeneity of the olivine and low-Ca pyroxene. Metallic Fe-Ni grains show no signs of alteration, consistent with weathering grade W0. The rock has been moderately shocked, equivalent to shock-stage S4; many of the olivine grains contain planar fractures and exhibit weak mosaic extinction. 
Specimens: Types specimens, 154 g MNCNA-AS, 2 g UCLA and 5 g CSIC. Most of the remaining material has been sold to private collectors.