12-15mm Graduated South Sea Pearl Necklace, Gold, Diamond Clasp. 18" The very essence of elegance, our graduated 12-15mm cultured South Sea pearl necklace showcases the incomparable luster of these gorgeous, luminous pearls. This impressive single-strand necklace features a diamond-accented ball clasp of 14kt yellow gold. Tahitian or South Sea pearls are unique and may vary. Pearl birthstones are the perfect gift for June birthdays.