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Agadez, Niger (18°40’30"N, 7°23’53"E)
H5 melt breccia
505 x 323 x 11 mm (19.75 x 12.75 x 0.4 in.)
4.72 kg (10.33 lbs)
H-melt breccias are extremely rare and this exemplary example, worthy of any museum, originates from a 400 kilogram meteorite that recently landed on Earth as evidenced by its freshness and lack of terrestrialization.
Impact melt breccias are among the most intriguing of all meteorites given their range of presentations. They are the result of asteroids slamming into target rocks in interplanetary space at cosmic velocity (approximately10 km/second). An extraordinarily powerful collision that results in the melting of a portion of the meteorite’s parent body, and its subsequent jettisoning into space. Impact melt breccias are among the most texturally diverse meteorites due to the variables of impact events including the speed and angle of the impactor, the type, amount and the flow of the melted target and the size, shape and abundance of the unmelted inclusions.
Such variation can even occur in the same meteorite. As described in the Meteoritical Bulletin, the journal of record, Tassédet 004 evidences 'considerable variation in petrography and clast size.' The black, roundish clasts seen suspended throughout the matrix are surrounded by lighter-colored quenched melt and igneous-textured microporphyritic melt domains. The black clasts show an even distribution of metal and sulfide and significant porosity as vesicles 10 to 200 μm, some with euhedral grains protruding into the voids.
More simply expressed, this is a one-of-a-kind, massive, complete slab of a meteorite delimited by its natural exterior surface that would have been an impressive H-chondrite — had it not experienced a cataclysmic impact in space resulting in the unique and striking showpiece now seen.
Provenance: Dr. Lawrence Stifler Collection of Meteorites, Brookline, MA.
