El Médano 498 (EM 498)        24°44.806’S, 70°21.179’W

Antofagasta, Chile

Find: 2019 Nov 23

Classification: Ordinary chondrite (L5-6)

History: While searching for meteorites, Vincent Stelluti recovered this stone on a slope of about 2% from the bottom of a local hill composed of gravel, stones and sand. The stone was sunk into the ground for about 1 cm.

Physical characteristics: A 332 g individual stone that appears generally brown, with a part of its surface retaining a very eroded fusion crust. The shape is roughly that of a leaning and truncated square pyramid. The base, which was sunk into the ground for about 2 cm, is rough while the part exposed to the wind is smooth with mature desert polish. Physical properties: Bulk density: 3.28±0.03 g/cm3; Grain density: 3.30±0.01; low porosity; magnetic susceptibility log χ (× 10^-9 m³/kg) = 4.36.

Petrography: Cut surfaces show a weathered brown matrix bearing dispersed metal grains and lighter-toned clasts up to 1 cm size, which appear to be of a higher petrographic grade. In thin section, the bulk of stone consists of chondrule fragments and few intact chondrules which are not well delineated within a finely recrystallized matrix. A few chondrules are as large as 2 mm. Olivine and pyroxene in thin section typically show undulatory extinction and planar fractures. Metal and sulfide occur as isolated grains which are interstitial to the chondrule fragments and matrix silicates.

Geochemistry: EPMA: olivine Fa_24.83±0.31 (n=10); Ca-poor pyroxene Fs_21.03±0.86Wo_1.64±0.24 (n=9)

Classification: Ordinary chondrite: L5-6 (S3) W2. Chondrule moderate to poor definition and recystallized matix suggest petrographic grade 5 for the bulk meteorite, consistent with limited range of olivine EPMA compositions. Lighter-toned clasts seen in cut surfaces appear to be of L6 chondrite.

Specimens: Type specimen: UWO; Main mass V. Stelluti