'Costume jewelry' bought in London turns out to be real, and really valuable

The large 26.27 karat diamond could be worth hundreds of thousands of dollars. (Sotheby's via AP)

It was an almost gaudily large piece of costume jewelry picked up for about $15 in the 1980s, and its owner apparently liked it—she "would wear it out shopping, wear it day-to-day." She almost certainly likes it much, much more now.

The ring, bought at a car-boot sale (akin to a flea market) in west London some three decades ago turns out to be a 26.27 carat white diamond, and it's expected to fetch as much as $450,000 when it's auctioned by Sotheby's on June 7, reports the Guardian.

Jessica Wyndham of Sotheby's says the unidentified owner assumed it wasn't real because it apparently didn't sparkle as a diamond tends to and was in a "filthy" mount.

The BBC reports those characteristics actually just stemmed from the reality of its age: It was likely cut in the 19th century. "With an old style of cutting ... the light doesn't reflect back as much as it would from a modern stone cutting," explains Wyndham.

"Cutters worked more with the natural shape of the crystal, to conserve as much weight rather than make it as brilliant as possible."

This article originally appeared on Newser: She Bought the 'Costume Jewelry' for $15. But It Was Real

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