875 21K Gold Pendant w/ Blue Marbleized Cabochon Pendant & 10K 18" Chain

875 21K Gold Pendant w/ Blue Marbleized Cabochon Pendant & 10K 18" Chain - The pendant is marked '875' (21K Gold) plus two Hallmarks. I don't know what the vibrant turquoise blue marbelized cabochon is made of (it looks as some kind of plastic from the flat white side). Pendant is 1.5" L X 1" W - The fine link chain is marked 10K and is 18" - Total weight 4.27g