Accrodting to Ortiz Diaz (2009), metallurgy was probably introduced to the area since the 8th century,as the rest of Mesoamerica, but production did not intensified until the post-classic period. There are three main regions in the state that have been documented to work metallurgy, the Mixtec and Zapotec of the Mixtec area and the central valley of Oaxaca, as well as the Chinantecs and highland Zapotecs of the Northern Sierra of Oaxaca. They primarily worked with gold, and silver (as the beautiful examples from Monte Alban tomb 7 showed), but also with copper. Apparently, as with the rest of Mesoamerica, Mixtecs may have learned the craft from two areas of development, Peru and Colombia, although the mode of exchange still debatable. The Mixtecs were really good at the lost wax technique, which they use to created beautiful luxury goods, such as all kinds of jewelry like pendants earrings, pectorals, as well as copper bells