The sculpted heads of the Olmecs are made from a variety of materials, some of which are an indication of extensive trade. First, the Olmec priest-rulers had sculptors use Basalt blocks as heavy as 18 tons to create large helmet heads, figurines and animal statues (von Sivers, Desnoyers, and Stow 137). Next, Olmec sculptors used clay, jade, serpentine to construct figures. Furthermore, since jade and serpentine were not available within 200 miles of San Lorenzo it has been concluded that San Lorenzo was not an isolated urban center, instead wielding far reaching trade connections (von Sivers, Desnoyers, and Stow 137).
