The Campo del Cielo impact is believed to have occurred approximately 5,000 years ago. The Campo strewnfield is roughly 18 km (11 miles) in length and includes at least 25 distinct craters. It is one of the larger known strewnfields on Earth, and perhaps the single biggest crater field. It is also one of the largest impacts from which actual meteorite specimens have been recovered. The heaviest single mass from the fall weighs 37 tons. Known as “El Chaco,” it is regarded as a national treasure and remains in Argentina where it originally fell. Another large mass, known as “Otumpa” and weighing an estimated 1,000 kg (2,204 lbs) was discovered in 1803. Due to a shortage of terrestrial iron, the Otumpa mass was transported to Buenos Aires where attempts were made to fashion it into weapons for use in the war against Spain. Some of this iron was employed to make the barrels of two pistols that were presented to United States President James Monroe, but the bulk of it (now reduced to 634 kg) eventually made the long sea journey to England, where it became the first large meteorite to be displayed at London’s British Museum.
Numerous additional masses have been found over the years and Campo del Cielo has one of the longest and most interesting terrestrial histories of any iron meteorite. It is a polycrystalline, coarse octahedrite and cut specimens often show inclusions of silicate-graphite-troilite.