The region which produced most gold was the province of Zacatula, on the Pacific coast some 10-12 days’ journey from Tenochtitlán, where the Indians used gourds and small wooden troughs to pan gold in the river beds. The same method was employed in the Tuxtepec district of Oaxaca. We know from early Spanish sources that gold was also panned on the east coast ,where Grijalva describes how the prospector picked out the grains of gold and stored them in his mouth until he was ready to melt them down on the spot using pottery vessel on a fire which he blew up by means of tubes made of hollow reeds.

No tin object has yet been found in the Valley of Mexico, but four lip-plugs made of cast tine are known from Teloloapan in the state of Guerrero. This is very near to Taxco where the ore deposits were exploited in pre-Spanish times, and analysis shows that the metal of the lip-plugs must come from a smelted ore, probably cassiterite, which is still to be found in the area. No crucibles, furnaces, or slag have yet been discovered, but tin can be extracted from cassiterite by packing the ore between alternating layers of wood and charcoal and then heating it to about 1,000 oC in a pot positioned so a to catch the natural draught.

For working metal the Aztec smith used a furnace heated by charcoal, the draught being supplied by a man blowing through a tube into the embers (52). Copper was added to gold to produce an alloy called tumbaga which was cheaper than pure gold, but could be treated to give the appearance of the more precious metal. Solder was made by mixing copper with silver. Copper and tin were alloyed to make true bronze, although the Aztecs do not seem to have realized its superiority over pure copper and showed little sign of taking the technological step which led to the development of a Bronze Age in the Old world.