Several groups along the Pacific coast of Ecuador, the Caribbean coast of Colombia, and up the Cauca and Magdalena rivers expand their territories and subsequently form chiefdoms. Large quantities of art objects are produced by specialized skilled craftsmen for the elite, who control the resources and productive processes, including assortments of personal adornments in bone, shell, semi-precious stone, and precious metal. Ornamented ceramic vessels, often in the shape of human or animal effigies, as well as stone and ceramic sculptures, some of considerable size, are thought to be evidence of ritual practices and complex religious beliefs. Gold is worked by many groups in Colombia.