17 - Aletai Meteorite Slice

Aletai Meteorite Slice An enormous etched slice from the famous Aletai meteorite, discovered in China's far northwestern Xinjiang Uyghur Autonomous Region (XUAR). Featuring the beautiful and clearly visible Widmanstätten pattern on both sides ; this pattern is unique to meteorites and found nowhere else on Earth. displaying kamacite bands with widths ranging from 0.9 to 1.8 mm and an average of 1.2 ± 0.2 mm. It is a sawn specimen of the Aletai iron meteorite (coarse octahedrite) and belongs to the very rare chemical group IIIE-an (i.e. chemical group IIIE with anomalous properties). At present, only two meteorites fall into this group. Different from other IIIE members, Aletai irons are characterized by higher Au and Co contents and unexcepted Ir contents that do not fall on extrapolation of the Au-Ir trend of the other IIIE irons. Overall, by combining geochemical data with petrologic observations, we concur with the conclusion of Meteoritical Bulletin 105 that Aletai is an anomalous IIIE iron. The composition of Aletai irons is so unique that no other samples in the world meteorite collection are comparable. The Ulasitai meteorite consists mainly of kamacite (76 vol%), taenite (10 vol%), and plessite (10.6 vol%) with less abundant schreibersite (3.4 vol%) and minor troilite, cohenite, and daubréelite. Weight: 4.8 kg. LOCATION: Altay Prefecture, Xinjiang, China (45° 52' 16"N, 90° 30' 17"E) Size: 60 x 40 cm. PROVENANCE: IIIE-an, Iron Meteorite. German Private Collection NOTE: – Aletai is a member of one of the smallest subgroups of iron meteorites in the scientific literature, with only 16 IIIE meteorites on record. And of these 16, Aletai is one of only two that have anomalous chemical abundances, containing the highest concentration of gold in the IIIE group. – Aletai also contains a relatively large amount of iridium, the second densest element in existence. Because the amount of iridium found in meteorites is often much higher than that found in the Earth's crust, it was the unusually large amount iridium present at the 65 million-year-old Cretaceous-Paleogene boundary that led scientists to believe that a massive meteorite impact was responsible for the extinction of the dinosaurs and many other life forms 65 million years ago. – The entire mass of Aletai is close to 100 tons, and a 28-ton Aletai specimen is the 5th largest single meteorite ever found on Earth. The strewn field was approximately 500 kilometers long. The shower of meteorite fragments were spread out over such a large area that specimens were given a variety of different names, 'Armanty', 'Xinjiang', and 'Ulasitai', primarily names of cities they were found nearby. As it has now been determined that each of these meteorites originated from the same event, they have all been renamed Aletai.