Lavras do Sul        30°48’S, 53°54’W

Rio Grande do Sul, Brazil

Found: 1985

Classification: Ordinary chondrite (L5)

History: A single mass weighing ~1 kg was found in a pebbly streambed near the town of Lavras do Sul by Prof. Picada of the Geosciences Institute, UFRGS. He gave it to his colleague Dr. Ary Roisemberg. Geologist Heinrich Frank contacted Dr. Hardy Grunewaldt after seeing the specimen in one of Dr. Roisemberg’s lectures

Physical characteristics: The 10 x 5 x 6 cm stone is completely fusion crust-covered . The interior shows brown spots due to weathering. The sample investigated in MNRJ is 67 g.

Petrography: (M.E.Zucolotto, MNRJ; L.L. Antonello, CBPF) The meteorite shows a few well-defined chondrules and fragments dispersed in a recrystallized matrix. The best-preserved chondrules are RP and BO. The chondrule sizes vary, mostly between 0.5 to 2.0 mm. Opaque phases are kamacite, taenite, troilite and tetratenite. The latter is observed as a thin layer that borders taenite and plessite. Kamacite is mostly polycrystalline and in some cases the plessite shows pearlitic structure bordered by tetrataenite. Sulfides are abundant and are mainly present as single grains. In places small plagioclase grains (partially isotropic) are observed. Some oxide veins as well as iddingsite penetrate along olivine fractures. Minor oxide is present around some metal grains. Melt pockets are scarce and small. Olivine grains have rims with planar fractures but clean cores, in which weakly mosaic and/or undulatory extinction is observed.

Geochemistry: (M.E.Varela, ICATE; R. Scorzelli, CBPF) Mean compositions are olivine (Fa₂₅) and low-Ca pyroxene (Fs_22.6).

Classification: Ordinary chondrite (L5); S3-4; weathering W1

Specimens: 57 g plus three thin sections are on deposit in MNRJ. Main mass with Dr. A. Roisemberg, UFRGS.