Slag from Dun Creich, Sutherland

01 June 2020

News Type:

Find of the Month

Iron slag is a common find in the Highlands. These examples were found at Dun Creich, a vitrified hillfort in East Sutherland on the Dornoch Firth.

The slag is a byproduct of smelting iron ore or bog iron, and therefore dates to a time when iron production occurred, sometime after c. 800 BC. However, smelting occurred into the post Medieval period, so other dating criteria are needed. Fortunately smelting requires hot fires, and often charcoal is discovered along with the slag, and in some cases the furnace bases. We have good dated examples of slag from Highland sites from a number of places.

A good overview on the processes from smelting to smithing, and the evidence resulting from each, can be found in a discussion of the iron slag from Portmahomack (Spall & Mortimer 2016) or Dornoch (Coleman and Photos-Jones 2008, 14ff). The iron ore is heated to create an iron bloom, with the slag being the waste product. The bloom must then be smithed, heated and hammered to be made into objects. In some cases hammerscale, by products from smithing, can be identified, and indicate workshop activity even if no structures survive.

In some areas of the Highlands charcoal burning platforms have been discovered located near to bloomeries, suggesting that the industrial activities were located near to charcoal producing areas. But as the excavations at Portmahomack showed, smelting appears to have also occurred in settlements where charcoal would have been imported. Charcoal could also be made from peat.

No dating has been undertaken at Dun Creich, although its multiple walls suggest possible different phases. In the centre, ruins of a castle said to have been built in the 13^th century survive, so the slag could date anytime from the Iron Age onwards. The hillfort is vitrified, where in the past, probably the Iron Age, a fire occurred so hot that it melted the rocks.

The slag fragments are in Historylinks Museum, with information about them on the Historylinks Image Archive.

Further information

Coleman, Russel and Photos-Jones, Effie 2008 ‘Early medieval settlement and ironworking in Dornoch Sutherland: excavations at The Meadows Business Park’, Scottish Archaeological Internet Reports 28.

Spall, Cecily with Mortimer, Catherine 2016 ‘Digest 6.9. Iron-working slags’, in Carver, Martin, Garner-Lahire, Justin, and Spall, Cecily 2016 Portmahomack on Tarbat Ness. Changing ideologies in north-east Scotland, sixth to sixteenth century AD, Society of Antiquaries of Scotland: Edinburgh, D107-D111. (Electronic copy available from Society of Antiquaries of Scotland website).

HER record for Dun Creich MHG10024

Historylinks Image Library no. 7695