Portable system of energy dispersive X‐ray fluorescence was used to determine the elemental composition of 68 pottery fragments from ‘Sambaqui do Bacanga’, an archeological site in São Luis, Maranhão, Brazil. This site was occupied from 6600 BP until 900 BP. By determining the element chemical composition of those fragments, it was possible to verify the existence of engobe in 43 pottery fragments. Obtained from two‐dimensional graphs and hierarchical cluster analysis performed in fragments of stratigraphies from surface and 113‐cm level, and 10 to 20, 132 and 144‐cm level, it was possible to group these fragments in five distinct groups, according to their stratigraphies. The results of data grouping (two‐dimensional graphics) are in agreement with hierarchical cluster analysis by Ward method. Copyright © 2011 John Wiley & Sons, Ltd.