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." 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. This article originally appeared on Newser: She Bought the 'Costume Jewelry' for $15.

Source: Fox News May 22, 2017 20:20 UTC