PREHISPANIC METALLURGY OF NORTHWEST ARGENTINA. THE STUDY OF CU MELTED DROPS FROM THE RINCÓN CHICO 15 SITE

L. R. GONZÁLEZ; E. CABANILLAS; G. A. GLUZMAN

Río de Janeiro

Congreso; 17th International Microscopy Congress; 2010

Sociedad brasileña de microscopía y microanálisis

After the X Century AC and before the European conquest, the native populations from Northwest Argentina developed an intense production of bronze (copper and tin alloy) with own particularities in the Andean region. The archaeological place named ?Sitio 15? in Rincón Chico, Catamarca province, is one of the most amazing places connected with the Northwest Argentine metallurgical production. Fourteen radiocarbon analysis have shown that the metallurgical activities begun in the X century and continue till the XVII, increasing the production scale contiguously without large changes in the technological style of production. We have reproduced in lab the probable conditions of mineral reduction to compare with the archaeological ones. Crucibles were filled with both mineral and wood charcoal from the same geographical region. Drops of metal were obtained. We have studied some of these drops by energy dispersive analysis EDS and X ray diffraction XRD and we compared them with the archaeological ones. The two materials, the one laboratory manufactured and that found in Sitio 15, have similar external aspects. Clearly the founded sphere with Cu on its surface implies that it might come from an technologic man made elaboration. The EDS analysis showed that this material has suffered the action of corrosion and that some soil components have entered the sample. We are certain that the Sn has been introduced volunteered, because no minerals with Sn are in nature. The interaction with soil is hardly evidenced because the difference in EDS results between centre and peripheral sites. The spherical form comes from a quick cooling process were the surface tension and the surface energy play important role. The lab-made ones might have been formed by nucleation of fine drops of copper appeared during the reduction process in crucibles, the found ones might have been formed during the same process during crucible reduction or might come from dropping metal.