Gibeon, Hardap Region, Great Namaqualand, (South West
Africa) Namibia
See specimens below.
Type: Iron (IVA) fine octahedrite
Basic Information
Location: Latitude 25 degrees 20 minutes South, Longitude 18 degrees East.
Structural Class: Fine octahedrite, Of (= octahedrite, fine), 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 times.
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, located on the east side of the Great Fish River. 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 that the Gibeon meteorite consisted primarily of large masses, and that smaller pieces like those found at Canyon Diablo, Odessa, and Sikhote-Alin, were unknown. Buchwald speculated that additional exploration might reveal smaller specimens. Additionally, it has been speculated that many of the 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 detectors, meteorite hunters will locate a substantial number of smaller specimens in the future.
Composition and Mineralogy
The chemical composition of the Gibeon is:
90% iron
8% nickel
0.4% cobalt
0.04% phosphorus.
The minerals identified in Gibeon meteorites 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.
Etched Gibeon meteorite specimens usually display a fine Widmanstatten structure (fine octahedrite). Oxidization (rusting) is usually not a problem with Gibeon specimens, due to the high Ni content of the meteorite. Taenite (Fe,Ni), is the source of the nickel. Troilite inclusions can be seen on all of the specimens listed below, though some of the Troilite inclusions are very small. Item D has unusually rich amounts of Troilite.
See the table at the bottom
of the page for definitions of the abbreviations in the PREPARATION column.
References: 1. “Iron Meteorites”, V. F. Buchwald, Vol. 2, P. 584-593 (1975). 2. “Catalogue of Meteorites”, 5th Edition, M. Grady, The Natural History Museum, P. 214 (2000). 3. “Meteorites From A to Z”, M. Jensen et al, 2nd Edition, P. 48 (2004).
4.
“The Meteorite Market”,
www.meteoritemarket.com/GNinfo.htm
Preparation: ET = etched w/ Widmanstatten pattern NE = natural edges FS = full slice POL = polished surface PS = part slice |
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