Among the treasures of Postclassic Mesoamerica, few objects rival the turquoise mosaic masks and effigies produced by Mixtec lapidaries and passed into Aztec ritual use. The British Museum's double-headed serpent is the exemplar: a carved cedar body sheathed in roughly 2,000 individually cut turquoise tesserae, set tile by tile in pine resin, with red thorny-oyster shell marking the gums and white queen-conch shell forming the teeth. This design system channels that object directly — a near-black substrate reading through fractured seams of blue-green stone, broken only by flashes of shell-red and shell-white. It is ornament built from thousands of small, deliberate decisions, not a single smooth surface but a jewel skin stretched taut over darkness.