(IDEX Online) - A British retiree who almost binned an item of worthless "costume jewelry" was stunned to find it was actually a genuine 34-ct diamond, worth up to $2.75m.The unnamed 70-year-old was clearing her house and took it to be valued, along with other pieces she'd picked up over the years, at swap meets. She had no idea where she bought it or how much she paid.Featonby's Auctioneers, in North Tyneside, had the gem graded by HRD Antwerp as 34.19ct round brilliant-cut natural diamond, H color, VS1 clarity with a triple excellent cut grade.It will be auctioned on 30 November with an estimate of $2.2m to $2.75m."We saw quite a large stone, bigger than a pound coin, and I thought it was a CZ [cubic zirconia], auctioneer Mark Lane told the BBC."She told us she'd been having a clear-out and that it nearly went in the bin before her neighbor suggested bringing her items to us to get valued."It sat on my desk for two or three days until I used a diamond tester machine. We then sent it off to our partners in London before it was certified by experts in Antwerp."Pic courtesy Featonby's Auctioneers