jade, jadeite, fei cui, Guatemala, gems, Mesoamerica

Foshag presents a comprehensive mineralogical study of Guatemalan jade based principally on archaeological objects and rough material from Guatemala and neighboring Mesoamerica. After reviewing the historical terminology and early references to jade, he discusses its probable geological source, noting the close association of jadeite with serpentinite and identifying the Motagua Valley–Sierra de las Minas region as the most favorable area for its occurrence, although no primary jadeite outcrop had yet been located. Chemical analyses demonstrate considerable compositional variation, ranging from relatively pure jadeite through albite-jadeite and approximately equal mixtures of jadeite and diopside to dark chloromelanite, and are compared with jadeites from Burma and other localities. Optical properties, refractive indices, X-ray identification, texture, color, and associated minerals are described as practical means of distinguishing these materials. Foshag also establishes several types of Guatemalan jade based on mineralogy and appearance, relates them to archaeological periods and sites, discusses other minerals mistaken for or used alongside jade, and examines indigenous lapidary techniques including sawing, drilling, grinding, polishing, and perforation. Published originally in Spanish in Antropologia e Historia de Guatemala, Vol. 6, No. 1, 1954. An English translation was published in 1957.