The 22-pound meteorite was examined under x-ray fluorescence scanning which determined that it was composed of 88 percent iron and 12 percent nickel (a metal that is relatively rare on Earth).
This January, southern MI experienced a meteor flash that showered fragments of space rock all over Livingston County.
Scientists studied this space rock at Central Michigan University.
The rock, which at the time was used to prop open doors, was taken by the farm's new owner when he eventually sold the property, and only just got around to seeing if it was actually a true meteorite.
He was inspired to have it checked out by the university after a rise in meteorite discoveries in MI.
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On 1 October the price range was narrowed even more to between £18.50 ($24.03) and £20 ($25.98). It sold 5,117 cars in 2017, while revenue grew 8 percent in the first half this year.
The farmer told him it was a meteorite, that it was part of the property and he could have it.
The man, who has asked to remain anonymous, knew the 22-pound rock came from outer space ever since he bought the house in 1988.
The Smithsonian and another museum in Maine have already expressed interest in the rock, and Sirbescu called it "the most valuable specimen I have ever held in my life, monetarily and scientifically". He went on to say that in the 1930s he and his father saw it come down at night on their property "and it made a heck of a noise when it hit". For the past thirty years, he has used it as a doorstop and sent it off to school with his children for show-and-tell.
The chunk of iron-which was confirmed as a space rock by the Smithsonian Institution in Washington, D.C. -is the sixth-largest meteorite ever found in MI, according to the museum. But earlier this year, the man heard about people selling small pieces of meteorites for substantial sums of money. The Smithsonian considered buying the meteorite for display.
A mineral museum in ME also was considering buying it, and the owner herself - a collector - said she might purchase it.
And geologist Mona Sirbescu said she "could tell right away that this was something special".
"I said, 'Wait a minute". As CMU notes, the man has pledged to donate 10% of the sale price to the university as a token of gratitude for helping him identify it.