What can iron slag tell an archaeologist?

The article is devoted to the archaeological iron slag. One of the most serious problems in russian archaeometallurgy is that iron slags have been ignored by russian archaeologists as a source of information. Russian researchers are too ready to draw conclusions about the function of the furnace (smelting or smithing), but the lack of knowledge about slag typology leads to confusing smelting and smithing waste, so many conclusions are no proof. Most russian articles don't contain the essential data such as: archaeological context, amount and weight of discovered slags, typology of slags, chemical composition etc. Unfortunately, many slags are thrown out in the field and are not included in the archaeological assemblage. For these reasons, purpose of the article is describe basic scientific knowledges which are "encrypted" in the archaeological slag. During the work the authors came to the following conclusions. Firstly, iron slags can be treated as reliable indicators of existing of iron smelting or smithing process on archaeological site. Slags prove ironmaking much better, than finds of iron artifacts or even blooms, because both iron tools and blooms theoretically could be imported while importing of slag on settlement is unlikely and senselessly. Secondly, the investigation of slag always begins in the field, therefore individual documentation of archaeometallurgical residues is preferred, because it helps identify the concentration of iron production on the site and date remains in some cases. Thirdly, the amount and weight of the discovered slags is also important, because it allows to determine the intensity of ironmaking and reconstruction the role of iron production in economy of ancient and medieval people. Fourthly, the slag typology plays an important role in the study of ancient metallurgy. There are different types of slag. Each of them represents a certain stage of iron production cycle (smelting and smithing). In some cases morphology of smelting slag can help in the reconstruction of the shapes and dimensions of destroyed furnaces and also can indicate a type of furnace, for example, slag blocks and tap slags are formed in different types of furnaces. Some slags allows to know about smithing operation. Thus, spheroid hammerscale can indicate welding technologies, and biggest concentration of hammerscale flakes in excavation area provide us with information on the exact location of the anvil. Finally, chemical and mineralogical composition may reflect a quality of produced iron and indicate iron ore source for ancient and medieval metallurgists.

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