18-karat yellow gold. Faceted smoky quartz. Made in Italy. About Roberto Coin: Since founding his own company in 1977, Roberto Coin has rightfully gained fame as a tireless innovator, most notably for pioneering the use of three-color gold in 1978. His jewelry seems to capture the fluidity of his amphibious hometown, Veniceâforms and shapes meld, creating a sense of wholeness, the distinction between the timeless and the modern ever-blurred. Perpetually reinventing his personal style, Roberto Coin produces more than 600 unique jewelry models annually. Each piece includes a hidden 0.3 carat ruby, a signature of the designer.