Archaeologia Islandica - 01.01.2007, Síða 68

Arne Espelund
220029WR | ..— | ~| | | | | |
29-0713 FeOfQH)_____________________Goethite
Figure 9. XRD-diagram of bog iron ore found on top of the slag heap at Belgsá.
have studied the local traditions (Friðriks-
son pers.comm.). Seemingly the endo-
thermic reaction of the roasting process
2 FeOOFI = Fe203 + H20 therefore has no
major negative influence on the ironmak-
ing process, nor does sulphur in the ore
seem to be a problem at this site. In order
to have a closer look at roasting, ochre
ore found at Ormstaðir was analysed after
drying only at 120 °C and also after calci-
nation at 600 °C. The values for S as well
as P were below 0.01% in both samples.2
In Mid-Norway excavations of
bloomery sites have taken place over a
period of some 20 years. A negative cor-
relation between the formation of fresh
ochre ore and slag analyses has gradually
been obtained. The find of pieces of well
mineralized ore at Belgsá strengthens the
impression of good bog iron ore as a non-
renewable resource, created in a distant
past and to a large extent consumed. In
the Belgsá slag heap a piece of metal, lost
by the ironmakers and weighing some
40 g was also found. It was analyzed at
Molab in Mo in Rana, with the following
result as shown in Table 7. Both represent
an excellent quality of metal: not hard-
enable, but easy to forge and with good
mechanical properties. The contents of
detrimental P and S are very low. The
metal is also remarkably free from slag,
reflected in the low values for Mn and
Si in the first row. The two elements can
only be present as oxides in a slag.
The standard product of this
period in both countries was a split
bloom, weighing some 5-15 kg. Nor-
wegian archaeologists agree that such
blooms were taken up through the shaft
2 In Norway the storage place for roasted ore is often found when bloomery sites are studied by excavations. Such ore is red
and magnetic. In some cases a good correlation between finds of ore and slag has been found, in other cases the results were
divergent (Espelund 2004 a), very similar to the outcome of the studies in Northern Iceland. The author has not heard of a
find of fresh bog ore next to the fumace of a bloomery site, similar to the one presented above.
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