Marquise Shape 1.25 carat London Blue Topaz Ring Size 7 in Sterling Silver 1.25 carat total weight Gemstone. London Blue Topaz: 1 piece, Marquise Shape, 10x5 mm. Gemstone has a nice color. Ring has a top dimension of 1/4 x 7/8 inches and weighs 2.30 grams. Retails for over $69.99. Ring features top quality workmanship and a beautiful finish. Ring is in pure Sterling Silver and stamped .925.