Iron Meteorites

Meteorites are traditionally classified as irons, stones, and stony-irons. The "irons" are composed of nearly pure metallic nickel-iron. This makes it easy to classify them as extraterrestrial in origin because pure metallic iron almost never occurs naturally on the Earth - it is in the form of some oxide. Fraknoi, et al. comment " if you ever come across a chunk of metallic iron, it is sure to be either man-made or a meteorite." The stony meteorites are more common but harder to identify, often requiring isotopic analysis to be sure. The stony-irons, mixtures of metallic iron and stone, are much rarer.

The Casas Grandes meteorite, on display at the Smithsonian Museum of Natural History, has a dimension of perhaps 1.5 meters. It was found in Chihuahua, Mexico. The sliced section here shows it to be essentially solid metal in the interior.

A closer view makes it clear that this is solid metal! There are interesting lines and striations associated with the crystal formation.

The metal is so solid and so pure that it can be cut into slices! These sections are perhaps a centimeter and a half thick and some 70-80 cm across.

Australian Iron Meteorites

This is one piece of a large iron meteorite collection which left 13 impact craters in Australia. It is on display in the Smithsonian Museum of Natural History. It is thought to be about 10,000 years old. This fragment is about a meter across.