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Bog Iron and Iron Working in the Viking Period

The majority of domestic produced iron during the Viking Period was derived from bog-iron, a form of Iron consisting of hydrated iron oxide minerals such as limonite and goethite formed by precipitation of groundwater flowing into wetlands. In some parts of Sweden iron ore, in the form of a powdery ochre known as rauði (lit. ‘red earth) was used. In both cases, the raw materials were usually roasted to drive off moisture before being smelted. You can find an excellent description of the process on the Hurstwic website Iron Production in the Viking Age

Typical iron-bearing groundwater emerging as a spring
image: Wikimedia

Bog Iron
image: SandAtlas

The Snaptun Stone
image: World Tree Project
This stone was probably used to protect the belows from heat.

Hylestad Stave Church – Regin forging a sword
image: Wikimedia

Egil’s Saga tells how Egil’s father, Skallagrim, was a great blacksmith who worked bog-iron derived from the bogs at Raufarnes:
Skalla-Grímr var járnsmiðr mikill ok hafði rauðablástr mikinn á vetrinn. Hann lét gera smiðju með sjónum mjök langt út frá Borg, þar sem heitir Raufarnes. Þótti honum skógar þar fjarlægir. En er hann fekk þar engan stein, þann er svá væri harðr eða sléttr, at honum þætti gott at lýja járn við, – því at þar er ekki malargrjót, eru þar smáir sandar allt með sæ, – var þat eitt kveld, þá er aðrir menn fóru at sofa, at Skalla-Grímr gekk til sjóvar ok hratt fram skipi áttæru, er hann átti, ok reri út til Miðfjarðareyja, lét þá hlaupa niðr stjóra fyrir stafn á skipinu. Síðan steig hann fyrir borð ok kafaði ok hafði upp með sér stein ok færði upp í skipit. Síðan fór hann sjálfr upp í skipit ok reri til lands ok bar steininn til smiðju sinnar ok lagði niðr fyrir smiðjudurum ok lúði þar síðan járn við. Liggr sá steinn þar enn ok mikit sindr hjá, ok sér þat á steininum, at hann er barðr ofan ok þat er brimsorfit grjót ok ekki því grjóti glíkt öðru, er þar er, ok munu nú ekki meira hefja fjórir menn.
Egils Saga Ch 30

Skallagrim was a great blacksmith, and worked large amounts of bog-iron in the winter. He had a built by the sea some distance from Borg, at a place now called Raufarnes, where he thought the woods were not too far away. But since he could not find any stone there suitably hard or smooth enough for hammering iron on as there were nothing but beach pebbles, and fine sand along the seashore – one evening, when other were asleep, Skallagrim went to the sea, and pushed out one of his eight-oared boats, and rowed out to the Midfirth islands. There he dropped the stone anchor from the bows of the boat, then stepped overboard, and dived down to the bottom, and brought up a large stone, and lifted it into the boat. Then he climbed into the boat and rowed to land and carried the stone to the forge and laid it down before the smithy door, and always forged his iron on it. That stone is still there with a pile of slag beside it; and its top bears the marks of hammering. It has been worn by the waves and it is different from the other stones that are there. Four men today could not lift it.

The Anvil Stone at Raufarnes
image: Hurstwic – Iron Production in the Viking Age

These ruins are the possible site of the forge at Raufarnes
image: Hurstwic – Iron Production in the Viking Age

Four students from Northwestern University Segal Design Institute carried out a project in Iceland:
Skallagrim’s Forge: A visitor experience dedicated to Skallagrim’s anvil stone