Researchers have found rocks on a small island between Madagascar and the eastern coast of Africa, a discovery that has been described as mysterious for one very important reason — they shouldn’t be there.

The rocks in question, quartzite, were discovered by researchers at Columbia University, thanks to a grant from the National Geographic Society. They had heard about them from a number of different media reports, but were finally able to confirm the presence of the quartzite, which is usually found in areas that have high temperatures and pressures, for themselves.

“This is contrary to plate tectonics,” said Cornelia Class, a geochemist at Columbia University, in a blog post. “Quartzite bodies do not belong on volcanic islands.”

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