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1.7 grams. 15 x 7 x 5 mm.   Tektite



Cosimo writes:

Aouelloul is an impact crater in Mauritania. It is located in the Akchar Desert, part of the Sahara Desert, approximately 50 km southeast of Atar.

The crater is exposed, 390 metres (1,280 ft) wide and roughly circular. The rim rises up to 53 metres (174 ft) above the bottom of the crater. Sediments in the crater are approximately 23 metres (75 ft) thick. Its age is estimated to be 3.1 ± 0.3 million years (Pliocene).

Tektite is found around the crater, although very few meteorites have been found.

Glass found around the impact crater of Aouelloul is a kind of silicic tektite similar to Darwin glass. As such, it furnishes a useful test of theories of the origin of tektites. In the particular case of Aouelloul, the question is whether (a) the glass, in the form of a glass meteorite, produced the crater by impact, or (b) the crater, under impact from a meteorite, formed the glass. New data on silicate diffusion coefficients show clearly that the glass could not have formed from the sandstone during the few seconds of intense heating associated with an impact. The time required at 1800°C to homogenize the glass is estimated as several days. It sometimes contains nickel-iron particles. These were trapped in the glass at the time of the impact and are part of the impactor.

Often when a crater is very old none of the meteorite survives. But when particles are trapped in glass it is possible to know its geochemistry. Appears that Aouelloul glass is meteoritic in origin and thus implies a meteoritic origin for other tektites. There is never very much of this material on the market. It is pretty rare glass.