At around 10:30 on the 12th February 1947 eyewitnesses in the Sikhote-Alin Mountains, in the region of Primorye in the then Soviet Union observed a light descending through the sky which was brighter than the sun. This bright flash and the accompanying sound of the fall were heard up to 300km from the impact and a 20 mile (32km) long smoke trail remained in the sky for several hours.
Though large iron meteorite falls had been witnessed previously and fragments recovered, this was the first time in recorded history that a fall of such magnitude had been observed first hand. It was estimated that around 70 metric tonnes of meteorite material had survived the destructive passage through the Earths atmosphere and reached landfall.
As the meteorite entered the Earths atmosphere it began to break apart, at an altitude of around 5.5km it went through a violent explosion called an air burst. The fragments from this explosion then went on to create an elliptical strewn field approximately 1.3km across. The force of the impact was so great that the fragments not only created craters of up to 26m across but some of the fragments were driven deep into the trunks of matters trees. It has been estimated that prior to entering the Earths atmosphere, the meteor may have weighed as much as 100,000kg.
Specimens of this meteorite fall into two types.
Firstly there are the "thumbprinted” or regmaglypted specimens which as the name implies look like they have rounded indentations which resembles thumbprints. This type frequently show a fusion crust and signs of atmospheric ablation and probably broke away from the main mass of the meteorite quite early in the descent through the atmosphere.
The second type are aptly named shrapnel or fragmented after their physical shape and form. They look like sharp edged pieces of torn metal which is evidence of the violent fragmentation which took place during the airburst at altitude, although some made have
exploded and fragmented on meeting with the solid frozen ground at that time.