Suivi de la fusion expérimentale de la galène de Melle (79) par microspectroscopie Raman
Abstract
This paper focuses on the study (macroscopic and microscopic) of the transformation of classic silver ore (galena: PbS) and its evolution from a repository produced experimentally in a muffle furnace operating at charcoal. While the chemical reaction that leads from the sulfide lead bullion is identified for a long time, its reproduction in a reactor bottom furnace remains unsatisfactory and attempts to understand the transformation processes of the galena remain largely unsuccessful. This lack of mastery of the process blocks possible reflections on material balances and weight mining in ancient economies including matters related to the circulation of lead. Thus two great moments in this production line must be better understood: the roasting phase of galena and the reduction into lead. To reach these objectives, µRaman spectroscopy provides a complementary view of the macroscopy approach to processing the silver galena especially to identify the various chemical species of lead (oxides, sulfates, oxysulfates, carbonates) formed during the transformation of galena. The transformation of the mineral occurs in the following steps: appearance of elemental sulfur and sulfates in the first minutes; reduction of sulfates in favor of the emergence of lead oxides; further reduction of sulfates with the appearance of cerusite.