Information on the geological origin of raw garnet is a pre-requisite for the better understanding of garnet production and trade in ancient societies. The presented study is a first attempt to determine possible source rocks for the garnets found in the Sloinge excavation in southwest Sweden. It includes analyses of garnets from other excavations in Sweden and Denmark. It is also an attempt to demonstrate the strength and shortcomings of a mineralogical-chemical approach to test hypotheses concerning trade and mining in ancient societies. The chemical composition of garnets from both the excavations and from possible source rocks in southwest Sweden have been analysed with a scanning electron microscope equipped with an EDS-detector. In addition, literature data on garnet compositions in east-central Sweden are used for comparative purposes. The analyses show that the archaeological garnets all are almandine-rich and remarkably similar in composition, irrespective of their origin. This result indicates that an important trade with garnet from a few mines occurred during the late Iron Age. Possible and probable source rocks are garnet-amphibolites/mafic granulites which are common in southwest Sweden. (C) 2002 Published by Elsevier Science Ltd.