2.50 ct. t.w. Multicolored Sapphire and Prehnite Ring With Diamonds In Sterling Silver. Size 7 - Statement rings are having their say in a big way! Our bold cabochon prehnite ring glows green at the center, with 2.50ct. t.w. multi-hued sapphires and .10 ct. t.w. diamonds glistening all around. Sterling silver ring.