CRYSTAL HARRIS AUCTIONING OFF HEFNER’S $90,000 ENGAGEMENT RING

After calling off her wedding to 85-year-old Hugh Hefner  in June, Crystal Harris held onto her estimated $90,000 engagement ring.

But now that several months have passed, the 3.39 carat circular-cut diamond will be auctioned off at Christie's in New York City in October. The former Playboy model, 25, "couldn't bear to look at the ring anymore because it brought back bad memories," a source tells TMZ.