Basic Information
Location: Great Namaqualand, Namibia, Africa. Latitude 25 degrees 20 minutes South, Longitude 18 degrees East.
Structural Class: Fine octahedrite, Of, *Widmanstatten bandwidth 0.3 ±0.5 mm.
Chemical Class: Group IVA, 7.93% Ni, 0.41% Co, 0.04% P, 2.0 ppm Ga, 0.12 ppm Ge, 2.3 ppm Ir.
Time of Fall: In prehistoric time. We are looking for a better estimate. If you have one, then send it to us.
Location Map
Here is a map showing where the Gibeon strewn field is located:
History
The Gibeon Meteorite was first reported by Capt. J.E. Alexander in 1838. He heard of masses of native iron up to two feet square on the east side of the Great Fish River. While he did not see the masses himself, he was able to obtain samples for analysis. Undoubtedly, the natives in the area were previously aware of these occurrences, since they were found on the surface.
In the years following, Europeans established large cattle ranches in the area and recovered many more large meteorites. A 232 kg mass was recovered in 1857. Many masses between 100 and 500 kg were recovered in the years shortly after 1900. As late as the publication of the Handbook of Iron Meteorites in 1975, scientists were reporting the that Gibeon consisted primarily of large masses and lacked the smaller pieces like those found at Canyon Diablo, Odessa, and Sikhote-Alin. Buchwald speculated that greater knowledge might reveal smaller specimens or that smaller fragments may have been collected by natives and made into tools. It seems that lack of knowledge may have been the answer. In the past year or two increasing numbers of small Gibeon Meteorites have been exported. It may be that with modern metal detection equipment meteorite hunters will locate a substantial number of smaller specimens.
Composition and Mineralogy
The chemical composition of the Gibeon is:
90% iron
8% nickel
0.4% cobalt
0.04% phosphorus.
The minerals in the Gibeon are:
Kamacite, taenite make up 99%+ of the meteorite
Troilite (an iron sulfide) is common as nodules and in recrystallized
forms.
Chromite (chrome oxide) is found occasionally
Daubreelite is found in the kamacite.
Enstatite (a silicate mineral--pyroxene) is rare.
Tridymite (a silicate mineral) is rare
Impact of the Gibeon
The Gibeon was apparently a large meteorite that burst high in the atmosphere, as did the observed fall at Sikhote-Alin. The fragments collected show some of the same characteristics as the Sikhote-Alin specimens. Some pieces show shrapnel-like features and "cold working" (bending and hammering-like deformation). Other specimens show regmaglypts that look very similar to Sikhote specimens.
When Did the Gibeon Fall
The Gibeon fell in pre-historic times. Our best estimate is ---- years ago.
How Old Is the Gibeon
Radiometric dating places the age of crystallization of the iron-nickel metal in the Gibeon at 4 billion years.
Find Out More About Meteorites
These books will help you learn more about meteorites:
Rocks from Space by O. Richard Norton, Mountain Press, 1994. This book
covers just about every aspect of meteorites in a way that
the layman can easily understand.
Meteorites & Their Parent Planets by Harry McSween, Cambridge U.
Pr., 1987. Well written book for a layman with a technical
background.
Handbook of Iron Meteorites by Vagn Buchwald, U. of California Press,
1976. A very complete technical description of known iron
meteorites.
Let's Investigate Magical, Mysterious Meteorites by Madelyn Carlisle,
Barron's, 1992. A well done book for children, but written in a
way that even adults will learn from it.
*Widmanstatten Pattern: crystal like growth:
To form such a crystal pattern would require cooling a molten solution
of nickel and
iron at an extremely slow rate, about 1 degree Celsius per 1000 years.
Thus it takes millions of years to form such a pattern. Although many nickel
iron meteorites have *Widmanstatten patterns, each pattern is unique and
is controlled by the exact elemental makeup of the iron along with the
relative time of cooling. These crystals are diagnostic for meteorites
because they are practically non-existent elsewhere on Earth.
