BRAZIL - RN
Equilibrated Ordinary Chondrite H5.
The texture of the Macau meteorite is clearly chondritic, although crystallization has caused the diffusion between the boundaries of the matrix and the cores. The condrules are rounded and sometimes elongated with sizes ranging from 0.2 to 2.4mm (average of 0.6mm). Its internal texture is quite variable, including barred olivine, radial pyroxene and porphyritic cores. Source: Gomes & Keil (1980).
The mineralogy obtained through electron microprobe analysis in Gomes et al. (1977c) shows Olivine Fa19.0, pyroxene bronze Fs17.4 and metallic FeNi (kamacite and taenite) are the major constituents. With smaller quantities, we have the plagioclases Ab82.1 An12.5 Or5.4 and troilite. Accessory minerals include chromite, pyroxenes rich in Ca (diopsidium) and hydrated iron oxides, due to terrestrial weathering, mainly associated with metallic phases. Source: Gomes & Keil (1980)..
Based on the mineral composition, particularly olivines, pyroxenes and chromite, it is concluded that the Macau meteorite belongs to the chemical group H. Although the meteorite is oxidized by terrestrial weathering, the total chemistry is consistent with the group H. Assuming that all Fe2O3 formed by the weathering of FeNi, the recalculated analyzes show the characteristics of group H: total Fe is 26.27%, total FeNi is 18.14% and the Fe / SiO2 (0.72), Feº / Ni (9.76) and Fe ° / Fe ( 0.62). The uniform and homogeneous composition of olivines and pyroxenes, the poorly chondritic texture and the degree of recrystallization of the matrix indicate that the meteorite belongs to the petrographic type 5 of Van Schmus and Wood (1967). Source: Gomes & Keil (1980).
Not reported by the Meteoritical Bulletin Database. Listed by Derby (1888a, b) Oliveira (1931), Vidal (1936), Hey (1966) and with complete description given by Gomes et al., 1977c.
The Macau meteorite fell in the afternoon, around 5 pm (local time) in the city of Macau, state of Rio Grande do Norte, on November 11, 1836. The meteorite rain fell accompanied by noises such as detonation and luminous phenomena (a brilliant bolide visible more than 600km away from the fall site). In that fall, several cows in the region were killed and a large number of fragments of the meteorite were reported near the Assu River, despite the fragments having spread over a wide area. Source: Gomes & Keil (1980).
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