text: Only with the Incas would metals really come into practical use. At Machu Picchu and other sites, metal was used for bolas, plumb bobs, chisels, gravers, pry bars, tweezers, needles, plates, fish hooks, spatulas, ladles, knives (tumi), bells, breastplates, lime spoons, mace heads, ear spools, bowls, cloak pins (tupus), axes, and foot plow adzes.
  Nonetheless, they remained materials through which to display wealth and status. The characteristic importance placed on colour, which had led to some of the earlier developments, was still present (sun/moon association with gold/silver). Metals other than gold also had an intrinsic value, with axe pieces being of particular note in this regard. With the spread of metal tools by the Incas, it is thought possible that a more Old World use of metals would have become more common. In any case, as Bruhns notes, "[b]ronze can be seen as an expensive substitute for the equally efficient stone". However, sediment research in Bolivia has revealed that metals such as silver were smelted on a very large scale, thousands of tons, from late Tiwanaku to Inca times (1000–1530 CE), which suggests that the paucity of metal (particularly precious metal) at Inca sites is more likely caused by Spanish acquisition and export than by limited pre-colonial use.
  It has been claimed that the Inca Empire expanded into Diaguita lands in what is now north-central Chile because of its mineral wealth, but that view is rejected by some scholars.
  Further, an additional possibility is that the Incas invaded the relatively well-populated Eastern Diaguita valleys (present-day Argentina) to obtain labor to send to Chilean mining districts. The Incas influenced Diaguitas, who adopted Incan metalworking techniques.
  Farther south in Chile, Mapuche tribes within or near the Incan Empire paid tributes in gold. Incan yanakuna are believed by archaeologists Tom Dillehay and Américo Gordon to have extracted gold south of the Incan frontier in free Mapuche territory. Following that thought, the main motive for Incan expansion into Mapuche territory would have been to access gold mines.
  Among the Mapuche people of central and south-central Chile, gold had an important cultural significance that predates Inca contact.
  At the time of the Spanish conquest of Chile, Mapuches are reported by various chroniclers to use gold ornaments. According to historian Osvaldo Silva gold ornaments of the Mapuche of the Concepción area evidence some kind of interaction between the Mapuche and the Inca that may have been trade, gifts, or spoils of war taken from a defeated Inca army.
  Pre-Hispanic Mapuche tools are known to have been relatively simple and made of wood and stone, but a few of them were actually made of copper and bronze.