VSF 2010 Report - Nabo

slag fragments and pieces of smelting slag are more indicative of iron production than
ironworking. This is supported further by the number of ferruginous concretions recovered,
many of which appear to be small bodies of iron ore.
The identification of the sunken, stone-lined feature in Structure 3 as an ironworking
hearth should be reviewed more critically and revised in light of the smelting slag recovered
from this feature. The slag recovered from this context corresponds to finds 29, 40 and 61.
ID. [7012]
Mag.
Max. Dimensions (cm)
Min. Dimensions (cm)
L W D L W D
Count
Weight (g)
Undiagnostic 3 1.5 1.5 0.5 0.5 0.5 851 1152.8
Flowed 5 4 1.5 1.5 0.5 0.5 591 1167.6
Tap
Smelting 11 5.5 5 1.5 1 0.5 96 2515.5
SHB
Hammerscale - 16.8
Fuel ash
Technical vitrif. 4 3 1.5 1.5 1 0.5 17 45.9
Ferr. conc. 5.5 3 3 1 1 1 65 366.5
Charcoal 1 0.1
Other - 80.0
Total 1621 5345.2
Context [7159]
This deposit contained ten ferrous lumps. On initial inspection, their plano-convex shape and
red luster made them appear as SHB’s. Their density and heavy weight for their size
contradicted this first judgement. After removing a sample from one of the lumps, it became
clear that these were lumps of iron. A sample was extracted from each iron lump for further
metallographic and chemical analysis. Sectioning one of the iron lumps revealed irregular
voids within the metal substrate. These iron lumps, deposited together, represent a cache of
some 44kg of unused iron. The iron lumps were identified as partially refined iron blooms.
The internal voids exposed upon sampling revealed that the iron had not been fully
consolidated. However, all the lumps share a similar plano-convex, or flattish-oval shape,
revealing that they had all been partly worked. It is not clear, yet, whether these unrefined
iron blooms were produced at the site, or were transported to the site.
Other contexts
Throughout the assessment, many small sample bags containing archaeometallurgical and
other residues were examined. Some of these bags relate to contexts that were excavated,
although a large portion of them derive from the heavy residue fraction recovered by
flotation. They have been listed in the table below. The majority of these small slag
fragments exhibit no diagnostic features. Many of the small bags contained a substantial
amount of stone. It is difficult to provide further interpretation concerning the nature and
origins of these smaller deposits due to the lack of diagnostic examples.
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