Christie’s is offering an 8.17-carat diamond ring at an upcoming auction in New York, where it could fetch as much as $350,000. The jewel bears a round brilliant-cut, D-color, internally flawless-clarity diamond and is on offer without reserve. It will take center stage at the October 15 Jewels Online sale, the auction house said on Tuesday. Christie’s will offer over 260 lots, including pieces from well-known jewelry houses such as Bulgari, Car…