Meteorite Aletai – Xinjiang, China

Aletai Meteorite – Iron Wonder of Group IIIE

The Aletai meteorite belongs to group IIIE, which is a specific type of iron meteorite. This classification includes meteorites with certain chemical compositions and crystallographic structures. Meteorites in this group tend to show an octahedral structure, which means that when cut and polished, they reveal distinctive patterns known as Widmanstätten patterns. IIIE meteorites, such as Aletai, are characterized by the presence of kamacite (low-nickel iron) and taenite (high-nickel iron) bands forming the octahedral pattern.

Uniqueness of the Aletai Meteorite

Aletai is exceptional due to the highest concentration of gold among group IIIE meteorites and a significantly higher concentration of iridium compared to others in the same group. Since the amount of iridium in meteorites is much higher than in Earth's crust, the unusually high concentration of iridium found at the Cretaceous–Paleogene boundary 65 million years ago formed the basis of the theory that a massive meteorite impact may have been responsible for the extinction of the dinosaurs.

Discovery and Spread

The meteorite was discovered in 1898 in China’s Xinjiang region. The total mass found is estimated to be around 74 tons. The largest fragment weighs 28 tons, making it the fifth largest meteorite on Earth. The impact field covered an area of up to 500 kilometers, initially causing discrepancies in identification and naming. Different names like Armanty and Ulasitai were later unified under the name Aletai after chemical analysis.

Mineralogy and Visual Effects

An interesting feature is that when the angle of light changes, the reflectivity of the main alloys changes and the sample sparkles. This effect is typical for octahedral structures, but Aletai is especially striking due to the presence of mirror-bright inclusions of the mineral schreibersite.