Sterling Silver Blue Sapphire and Diamond Necklace (1.80 CT) 30 Day Easy Returns. Jewelry Gift Box Included .925 Sterling Silver Natural Sapphire stones are heat treated to remove color zoning, and improve color and vibrancy. No radiation, chemicals or health risks are involved in this process. This process is permanent. Blue Sapphire - 1.62 CT ; Diamond - 0.18 CT