From the Venetian Medallion Collection. Roberto Coin's 18K yellow gold necklace features delicate rolo chain suspending a bright red agate and diamond pendant.Roberto Coin signs each piece with a single ruby placed in a hidden position. Diamonds, 0.29 tcw Diamond color: GH Diamond clarity: SI1 Red agate 18K yellow gold Lobster clasp Imported SIZE Adjustable chain: about 17"-19"L Pendant: about 0.71"W ABOUT THE BRAND Jewelry designer Roberto Coin founded his eponymous line in 1996, with a strong emphasis on elegance and creative experimentation. Each piece is the result of a long creative process, taking inspiration from cultural influences and nature. Fine Jewelry - Roberto Coin Asset > Roberto Coin > Saks Fifth Avenue. Roberto Coin. Color: Yellow Gold.