Unique Antique Art Deco Platinum Diamond Black Onyx Necklace. This beautiful necklace has a unique art deco design and was made c. 1920. The necklace is set with 68 rose cut diamonds. For a total weight of 1.40 carats. The rose cuts are white and firey and average I color SI-1 clarity. From the top diamond to the bottom it measures 1-1/2 inches. The pendant measures 1- 1/8 inches wide. The chain measures 18 inches long. In the center of the pendant is a polished black onyx in a diamond shape. This is a beautiful antique art deco necklace sure to please any art collector. Excellent condition. Weight 7.7 grams.