Interpreting the chemical variability of iron smelting slag: A case study from northeastern Madagascar

Abstract

The archaeological remains of a metallurgical workshop were excavated at Amboronala (northeast of Madagascar/1000–1200 CE). The bulk mineralogical (X-Ray Diffraction) and chemical (X-Ray Fluorescence) data on ores, building materials, and slag are used to carry out a mass balance calculation. The results show an important variability from one smelt to the other, reflecting a poorly controlled process. During each smelt, a given amount of building material contributes to the formation of the slag, and the conditions of reduction allow the extraction of a given amount of metal. These two main factors influence the composition of the slag independently and variably. This find-ing allows to make some inference on the origin of the technique and the organization of the production can be made.