Angra dos Reis meteorite

The Angra dos Reis meteorite is the type specimen of the angrite group. It was observed when it fell to earth in 1869.^[1]

Discovery and naming

The meteorite is named after Angra dos Reis, a municipality of Rio de Janeiro, Brazil. It fell on 20 January 1869 into the bay where the water was about 2 m deep. Two fragments were found by a diver the next day.^[2]

Mineralogy

Although it is the type specimen of the angrites, Angra dos Reis is actually very different from most angrites. It is almost completely made from a rare form of pyroxene called fassaite. This makes it more like a pyroxenite than the typical angrite, which is similar to a basalt. The only other meteorite samples that contain fassaite are the Calcium-aluminium-rich inclusions found in the Allende meteorite. The reason for this exotic composition is thought to be partial melting of a chondritic precursor under redox conditions in which meteoric iron is unstable.^[3]

References