The Gibeon meteorites are displayed in the Post Street Mall, in Windhoek, and are some of the 120 specimens that have been found near the village of Gibeon near the town of Mariental. The meteorites are permanently fixed at the Meteorite Fountain, not far from the Independence Avenue entrance and were proclaimed a national monument on 15th February 1950.
The Gibeon meteorite shower is the most extensive meteorite shower known on Earth which covers a large elliptical area of some 275 by 100 kilometers centered on Brukkaros south of Mariental. Most fragments fell just southeast of Gibeon. To date, some 120 specimens with a weight of almost 25 tons have been recorded.
The Gibeon Meteorites occur partially embedded in rocks of the Karoo Sequence and calcretes of the Kalahari group. It has been calculated that a meteorite body, measuring roughly 4 by 4 by 1.5 meters must have entered the Earth’s atmosphere along a northwesterly trajectory and at a low angle of 10` to 20` from the horizon. This body fragmented while still high in the atmosphere, so that the fragments themselves suffered thermal alteration by melting of the outer surface.
This either covered the fragments in smooth outer layers, or was pulled off in places by the drag of the atmosphere, leaving an uneven mass with deep, spherical cavities on the outer surface. These well-developed thermal alteration structures prove that the fragments had an extended flight through the atmosphere before being deposited. The varieties of thermal and shock-induced microstructures of the Gibeon Meteorites are the greatest in the world an only matched by the Canyon Diablo Meteorite of northern Arizona.
The Gibeon Meteorites are classified as octahedrites, the most common type of iron meteorite, and consist entirely of taenite and kamacite, two different crystalline varieties of a iron-nickel alloy. Taenite (gamma-Fe with 8-55% Ni) and kamacite (alpha-Fe with 5.5% Ni) form alternating parallel crystal bands that are arranged in a triangular pattern. This pattern is the typical Widmannstatten structure, a characteristic feature of many meteorites. Besides iron, the main constituent, the Gibeon Meteorites contain an average of 8% nickel, 0.5% cobalt, 0.04% phosphorus, small amounts of carbon, sulphur, chromium and copper, and traces of zinc, gallium, germanium and iridium. The Gibeon Meteorite specimens range in size from one ton to just a view grams. A few rare tetrahedral and octahedral crystals have also been recovered, and probably resulted from the successive splitting off of thin kamacite lamellae along with the selective corrosion of intervening taenite layers.
Today, the known Gibeon Meteorites that have remained in Namibia are displayed in the Post Street Mall and at the museum of the Geological Survey of Namibia in Windhoek. A number of smaller pieces also form part of the reference collection of the Geological Survey of Namibia.