A mother-of-pearl doublet pendant necklace in sterling silver with diamond accents. From Ippolita. Diamonds: 0.18 ct. T. W. Sterling silver/mother-of-pearl/clear quartz. 16-18" adjustable. Lobster clasp. All gemstone carat weights (ct. T. W. Are approximate; variance may be. 05 carat. Gemstone Treatment and Care. Almost all gemstones and black diamonds have been treated to enhance their beauty and require special care. Imported.