An experimental approach for smelting tin ores from Northwestern Iberia

In the present work microstructural and chemical analysis of tin and slag that resulted from three smelting experiments reconstructing prehistoric conditions are presented. Cassiterite ores were collected from northwestern (NW) Iberian deposits and were smelted in a small open pit. Results show that the loss in tin can be very high, up to 80%, mainly as a result of volatilization of Sn species. The experiments show that using handmade leather bag bellows and clay tuyeres, temperatures can easily reach >1200°C. The tin produced was a very pure (Sn) solid solution, with the presence of dispersed inclusions or phases of various composition. These included FeSn and FeSn₂ intermetallics and small metallic W inclusions. Slags could be grouped into three types based on their physical characteristics, and bulk chemical analysis could relate each type as being a product from the reaction of ore material or a product from the reaction with the crucible material. Generally, it was found that in spite of very low recovery rates, the tin produced by this simple technique would have been adequate for a domestic small-scale production.