W1 or more
BRAZIL - MG
Equilibrated Ordinary Chondrite H4, slightly weathered by terrestrial oxidation.
The meteorite exhibits a pronounced chondritic texture with chondrules ranging from round to elongated in shape and diameter from 0.1 to 1.9mm (average of 0.5mm). The chondrules are very visible with their well-defined delimitation in the middle of the fine-grained matrix consisting mainly of microcrystalline material, which seems to recrystallize the previously glassy matrix. The internal texture of the chondrules is very varied, such as barred, radial, porphyritic and granular. Glassy material was also found inside the chondrules. Source: Gomes & Keil (1980).
According to Keil et al. (1978a), the meteorite mainly consists of olivine Fa17.2, pyroxene with low Ca Fs15.4 Wo3.0 and FeNi, with lower amounts of troilite and glassy material with varying composition. Accessory minerals include pigeonite Fs15.6, chromite, and pyroxene with a high Ca content. Hydrated ferric oxide, due to terrestrial weathering, was found around the FeNi metal phases. Source: Gomes & Keil (1980).
The composition of the olivine and pyroxene of the Conquista meteorite is very close to the final limit of the chemical group L, reaching the group H of the chondrites. The chemical composition of chromite also suggests classification as group H. This classification is confirmed by the total chemistry and the Feº / Ni (9.59), Fe / SiO2 (0.69) and Feº / Fe (0.64) ratios, as well as the total concentration of total Fe in the meteorite (25.3%) and total FeNi of 18.5%, considering that all the iron oxide III present comes from the terrestrial weathering that oxidized the present FeNi. The type 4 petrographic classification, according to Van Schmus & Wood (1967), is due to the slight variation in composition still found in olivine and pyroxene, the well-defined chondritic texture, the abundant presence of low Ca pyroxene twins and glassy material also found within the chondrules. Source: Gomes & Keil (1980).
Not reported by the Meteoritical Bulletin Database. A detailed study on the Conquista meteorite was carried out by Keil et al. (1978a).
The meteorite fell in the morning (6 am local time) on an unknown day in December 1965, at Fazenda da Mateira, in the Minas Gerais municipality of Conquista. The fall was accompanied by a loud noise and an impact well with a diameter of 1.5 m was formed. Many fragments are said to have been distributed around the well, but only the main mass of 20.35 kg appears to have been preserved. Source: Gomes & Keil (1980).
All information that does not have a specific source was extracted from the Meteoritical Bulletin Database.
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