Lady's 18K White Gold 3.90ct Rubellite and Diamond Fashion Ring. Ring Size: 6 1/4(Can be Resized to Fit Most Any Finger) Contains: 1 Cushion Cut Natural Rubellite. Weight: 3.90ct. 100 Round Brilliant Cut Natural Diamonds. Weight: 0.78cttw. A rare and beautiful almost four-carat Brazilian Rubellite placed in a diamond-set handmade 18K White Gold mounting. In yesteryear, these stones were very plentiful. Now almost the entire supply has dried up. When properly cut, the stone is even more attractive than a ruby. This stone is cut in the old fashion way, known as a cushion cut.