A detailed study of turquoise mosaic work from ancient Mexico, tracing early historical descriptions, colonial-era collection accounts, and the sourcing and lapidary techniques used to cut and set turquoise. It catalogs the forms decorated with mosaic—helmets, masks including skull masks, shields, ear ornaments, animal figures, deity representations, knife handles, and musical implements—illustrates notable examples from Chichen Itza and museum collections, and analyzes stylistic and technical variations. Plates, drawings, notes, and a bibliography accompany the descriptive catalogue and a concluding discussion of provenance and preservation.