Image copyright Central Michgan University

A US professor has established a rock used as a doorstop is actually a meteorite worth thousands of dollars.

Mona Sirbescu from Central Michigan University was asked by a local man to inspect the object he had kept for 30 years after finding it on a farm.

The 22lb (10kg) meteorite was the biggest the geologist had been asked to examine in her career.

The rock, which came down on farmland in Edmore, Michigan, in the 1930s, could be worth $100,000 (£77,000).

Most meteorites typically consist of approximately 90-95% iron.

What makes the meteorite found in Michigan unique is that it is 88% iron and 12% nickel.

"A piece of the early solar system literally fell into our hands," Dr Sirbescu said in a video made by the university to promote its discovery.

Dr Sirbescu sent a sample of the rock to the Smithsonian Institution in Washington DC, which confirmed her findings.

The renowned science centre is now interested in buying the rock, Central Michigan University said.

Meanwhile, the university has been using the meteorite as a teaching material.

The meteorite's anonymous owner is promising to donate 10% of sale proceeds to the university.

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