Precious metal recovery unit

Abstract

The lack of important silver and gold sources in Brazil before the finds in the region of Minas Gerais at the end of the 17th century is known. Information concerning the first gold finds reached the Portuguese capital in 1695 but it was only in 1697 that the first ship arrived at Lisbon harbour with a gold load identified in the documents as ‘Peruvian’ but supposed to be Brazilian.The first Brazilian mint was itinerant, and the first silver and gold coins were struck in Bahia from 1694 to 1698. In order to try to find out which metals were struck before 1698 in Brazil, we analyzed gold and silver coins issued by the first Brazilian mint, Bahia, and coins issued in Mexico and in South America—Peru, Bolivia, Colombia, Chile—as well as Brazilian gold ingots from different mining regions. Fingerprinting was done using several analytical techniques: 12 MeV proton activation analysis, moderated neutrons activation analysis and inductively coupled plasma mass spectrometry with laser ablation.We could show that in general the platinum group elements discriminate gold and that elements such as gold, indium and tin discriminate silver. The comparison of the Brazilian coins and ingots with the coins issued elsewhere in South America and Mexico showed that the gold and silver coins circulating in Brazil between 1694 and 1698 were mostly made from a mixture of metals from the main Latin American sources.