Meteor Crater, Arizona. It is also called the Barringer Crater, after the mining engineer who first suggested that it was formed by a meteor impact. It is about 50, 000 years old and is about 200 meters deep and 800 meters across. Several attempts to mine the iron- rich material of the meteor were made before a visitor center was built in the 1960's. Two new minerals - coesite and stishovite - were identified here; both are forms of silica created at high temperatures and pressures. In recent years the crater has been used for astronaut training & studies in planet comparison.