VSF 2010 Report - Nabo

Ferruginous concretions were identified throughout the assemblage. Many of these
lumps appear to be heavily corroded pieces of iron. Their amorphous shape and iron
hydroxide banding cause them to fragment and flake easily, also making it impossible to be
certain that they originally derive from metallic iron. Some pieces were tentatively identified
as nail fragments. Those ferruginous lumps that were confidently identified as nails were
separated and united with the collection of finds for further investigation; most of these
appeared totally oxidised and corroded bearing no existent metallic phases. Some ferruginous
concretions may also derive from amorphous metallic fragments such as pieces of bloomery
iron, showing no shape or form.
It is likely that some of these lumps represent pieces of reduced ore. The reddishpurplish
appearance of many lumps are common to roasted ores. Some of these lumps were
subsumed within, or adhered to, slag (in these cases, the weight recorded is not reflective of
the actuall ferruginous concretion identified, but the agglomerate itself). Further analysis, in
the form ox x-ray diffraction, would be necessary to confirm the identification of these pieces
of reduced ore.
Other
Any material not pertaining to the categories already described was identified as ‘other’. This
category mostly represents stone and lava. Some fragments of burnt bone were recovered
during this assessment, included within this category, which are highlighted in those contexts
concerned.
Results
Visual assessment
A summary of the results from the visual examination are provided here. A detailed
description of the count and weights of the residues examined are listed by context in
Appendix 3, each with a brief description and discussion. Some contexts containing
metallurgical residues (described in previous reports) were not examined during this
assessment. Those contexts that were not examined, though deemed relevant to the
investigation, are also included in Appendix 3.
In total, over 10,000 items were counted and examined. This figure does not represent
the actual number of pieces of slag recovered, as large quantities consisting of small
fragments were recovered in the heavy residue fraction by flotation. The total weight of the
archaeometallurgical residues assessed is nearly 160kg. Figure 3 illustrates the weight of
archaeometallurgical residues recovered for each context to allow for comparison and to
graphically highlight certain features of the overall assemblage.
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