Meteorite - CAMPO DEL CIELOFerrous Meteorite.
Structual class : Octaedrite , Og, band width 3,0 ±0.6 Widmanstatten.
Chemical class : Group I, 6,68% Ni, 0,43% Co, 0,25% P, 87 pages per minute Ga, 407 GES pages per minute.
Estimated fall date : between 4,000 to 6,000 years ago.
History : This meteorite was first discovered in 1576. A Spanish governor received blocks of iron from Indians who were convinced that they had fallen from the sky. The governor sent out an expedition under the command of Captain Miraval that brought back a few pieces of an enormous mass of iron that he called Meson de Fierro (large iron table).
The place of this discovery was Campo del Cielo (Field of Heaven), a name very well suited for a meteorite fall ! This area is a dry open plain with no other large rocks. These are ideal conditions to allow these meteorites to be found.
It wasn’t until 1770 that this meteorite was “rediscovered”. The Spanish believed that the material might contain silver. After treatment, it became obvious that it contained only iron.
A Spanish Navy Lieutenant extracted a specimen that he claimed weighed between 14 and 18 tons. It was baptized " Meson de Fierro ". This meteorite was left in place... and has never been found again.
In the 19th century, small meteorites were found in this same area. But it wasn’t until the 20th century that systematic explorations showed important iron masses, while still not finding the " Meson de Fierro ".
In 1992, the American meteorite collector and merchant, Robert Haag was arrested by Argentinian authorities while transporting a meteorite of 37 tons from the area. Haag had bought the mass from an Argentinian who had claimed ownership. Haag was released and this enormous meteorite remained in Argentina.
Craters : The largest meteorites from Campo del Cielo were found in and around a series of small craters in the south-west part of the of the principal field. The largest crater is 78 by 65 meters. Another smaller crater is 56 meters in diameter and 5 meters deep. A dozen craters were noted.
The principal masses were found in these craters. Scientists dated the carbonized wood found in these craters. Dates of 5800 years ago (+/-200 years) and 3950 years ago (+/- 90 years) were obtained. These dates conform with the Indian oral tradition that "iron fell from the sky."
Several of the meteorites of Campo are very rusted and corroded by earthly chlorides, however some have zones showing a crust of relatively fresh fusion. This is also an indication of strikes in the not too distant past.
Structure: Campo del Cielo is described as a polycrystalline octaedrite at 3 millimeter Widmanstatten bands.
The mass is composed of large crystals of Austenite of 5 to 50 centimetres. The structural study of this meteorite allows one to think that the original body was tabular in form and broke up upon it’s entry into the atmosphere.
Chemical : Campo del Cielo is classified in the group I, 6,68% Ni, 0,43% Co, 0,25% P, 87 p per minute Ga, 407 GES pages per minute, 3.6 p per minute Ires . The rest of its composition is exclusively iron. The important minerals are :
Kamacite : this iron and nickel alloy is that of about 90% of the crystals of centimetric dimension. The Neumann bands are common (communal).
Taenite and Plessite are the other constituants of the iron-nickel alloy. It is found in grains.
Schreibersite is present in small quantities.
Troilite is present in the graphite and silicate aggregats.
