1.00 Carat Sapphire and .30 ct. t.w. Diamond Necklace In 18kt Yellow Gold 18" - 1.00 carat sapphire flickers in a .30 ct. t.w. diamond-glazed frame of 18kt yellow gold. On a .5mm box chain with a lobster clasp. Pendant measures 1/4" in width and hangs to a length of just over 1/2".