Image source: Getty Images.Shares of jeweler Tiffany & Co. (NYSE: TIF) jumped 12.3% in November, according to data provided by S&P Global Market Intelligence , as a buyout and an analyst upgrade had investors cheering on the stock. Diamond-selling competitor Blue Nile (NASDAQ: NILE) agreed to a $500 million buyout offer, paying investors $40.75 per share in cash.