Meteorite Canyon Diablo – Arizona, USA

The Canyon Diablo meteorite struck about 50,000 years ago and formed Barringer Crater, also known as Meteor Crater, which is about 1.6 km in diameter and about 170 metres deep. This crater is located in Arizona, USA, and is one of the best preserved meteorite craters on Earth. The meteorite is named after nearby Diablo Canyon, located about 5 km west of the crater.

The meteorite was discovered in 1891 and has since attracted scientific interest due to its composition and the number of fragments found. Its fragments contain rare minerals, including diamonds, which were formed under extreme pressure conditions during the impact.

Classification and composition

Canyon Diablo is an iron meteorite of the IAB-MG type composed primarily of kamacite, an iron-nickel alloy (approximately 90%). It also contains 1-4% taenite, another iron-nickel alloy, and crystals of schreibersite and troilite. Often cohenite, which is an iron carbide harder than schreibersite, is present.

Samples that have been subjected to severe impact show evidence of partial melting, recrystallization, Neumann banding, and other deformation. One of the most significant effects is the transformation of graphite into diamond and lonsdaleite. These substances appear as dark masses visible on cutting. The diamond wheel shifts sideways when in contact with these materials.

Fragments

The Canyon Diablo meteorite broke into thousands of fragments on impact. The largest piece found is the Holsinger meteorite, weighing 639 kg, which is on display at the Meteor Crater Museum. Fragments larger than ten kilograms are rare, and those over 100 kilograms are few and far between. The total weight of the fragments found is estimated at more than 30 tonnes. On many meteorite fragments, especially those found on the rim of the crater, the Widmanstätten pattern was destroyed by the explosion that occurred when the meteorite hit the Earth.

History of mining

Daniel M. Barringer, a mining engineer and businessman, proposed in 1903 that the crater was formed by the impact of a large iron meteorite and applied for a mining permit for 640 acres around the center of the crater. He had ambitious plans to mine the metal, which he believed was buried beneath the crater floor. Based on the size of the crater, he estimated that the meteorite weighed 100 million tons.

At the time, the area around the crater was covered with about 30 tons of large oxidized fragments of the iron meteorite, leading Barringer to believe that much of the impactor (the body that formed the impact crater) was still under the crater floor. Barringer spent 27 years searching for a large meteoric iron deposit and drilled to a depth of 419 metres, but found no significant deposit.

The 1929 discovery

In 1929, astronomer F. R. Moulton, employed by the Barringer Crater Company, investigated the physical aspects of the impact and concluded that the impactor weighed only 300,000 tons and the impact generated enough heat to vaporize it immediately. Barringer died ten days after the publication of Moulton's second report.

The 1963 research

Scientists compared the crater to those created by nuclear tests and calculated that 1.7 megatons of energy would be needed to create it. This energy would be delivered by a 63,000-tonne body (a sphere about 24 metres in diameter) moving at 14.5 kilometres per second.

An estimated total of about 30 tonnes of specimens have been collected. It is further estimated that the fine-grained material around the crater contains 8,000 tons of iron, leaving about 55,000 tons to speculate on. Most of it has evaporated and some of it remains in the form of specimens in the area around the crater. After examining the area around the crater and mapping a large area northeast of the crater, it was found that there were small spherical droplets of condensed iron. Prior to the recent closure of the area to meteorite hunting, hunters with metal detectors were still finding significant numbers of specimens.