Mining in Medieval Sweden

The economic history of Medieval Sweden is entwined with the early development of proto-industrial iron works and mining in the region north of Stockholm. But when did it take off and who were the entrepreneurs?

There is no doubt smelting bog-iron was an important part of iron-age farming in Early Medieval Sweden. However, iron-smelting did not gain real importance until blast furnaces were adopted. But when was that?

Blast Furnaces

A medieval blast furnace was a tall oven with shafts several metres high and app 1-2 metres in diameter. In Sweden, the shafts were lined with a natural stone of clay mortar. This was reinforced with an encircling wall of heavier stone and fitted with an outer timber box. The area between the lining and the timber-box was filled with fine-grained material – often sand and soil. At the bottom were two vaults or passages running in towards the centre of the shaft. One was intended for blowing in air by means of water-driven bellows; the other was intended as the outlet for the molten iron and the retrieval of the slags.

Such blast furnaces were built alongside fast-flowing water courses and ideally located near the brink and near a deposit of rock-ore. On the other hand, it was nice if it might be built into a hill-side. This way, the workers were able to cart the brittle rock-ore and the charcoal up the hill and feed the furnace from the top.

As late as the 1970s medievalists believed that the Blast Furnace had been imported to Sweden from Northern Germany. However, today it is considered a local invention, which grew out of expereimentations carried out by local craftsmen.

Ironworks might be located inside villages. Typically, though, iron-works were constructed in the outfields or further into the outland or wilderness, whereever the geographical lay-out made it opportune.

Blast Furnaces in Sweden

It is estimated that there existed around 700 local blast furnaces in Sweden the middle ages; of these several hundred were located in the provinces of Dalarna and Västmanland. Of central importance here was the mining district around Norberg, which presented shallow and easily accessible iron ores. The district, which covers app. 1000 km2, is generally considered the first area in Sweden to have been exploited for iron ores. Inside this area more than a 1000 historical mining-related sites have been registered covering the whole production process.

In the Early Middle Ages (prior to AD 1000) this province was dominated by large iron-age farms, which controlled the production of iron from traditional smelting processes. These farms were worked by slaves. Sometime, around 1050 a period of expansion took off led by the descendants of these former dependants. The exact date of this expansion has been retrieved from studies of two samples of sediments from lakes in the center of the district, near Norberg. Data from these studies witness to an early expansion in forest grazing around Ad 1050, with more extensive forest disturbance from ca. AD 1180 accompanied by an increase in charcoal particles. From AD 1295 the evidence of mining and metallurgical activities are ubiquitous. From the 15th century and onward, remnants in the sediment records witness to a widespread proto-industrial activity in this region.

We may conclude that the extraction of iron from rock as opposed to bog seems to have taken off from around 1180.

These early iron-works were traditionally considered as communal projects and basically the end-result of the small settlements, which grew up around the homesteads in this expansionary period.

furnace at Nya Lapphyttan. Source Wikipedia — Driving the blast of air into the furnace at Nya Lapphyttan

Ing-Marie Petterson has most recently argued this model. In her opinion the iron-works could never have been established without the know-how of local craftsmen; she also considers the invention of the blast furnace in its Swedish form as the local result of smiths and other craftsmen experimenting with the construction of the traditional furnaces. One reason for this involvement of teams of local craftsmen were the need to have the process supervised for a long period of time. Simple put, a blast furnace had to be operated around the clock and for several months at a time.

Later, when the production reached it medieval high-water mark and iron and copper turned into the most important export-articles from medieval Sweden, it is possible to discern the intervention of more powerful political players. However, in her opinion, it was absentee landlords, living further south, who invested in the mining enterprises.

As opposed to this, Anders Törnqvist have argued that the medieval iron-works were simply started around this time by magnates – primarily representative of the kindred of the Folkungar – who sought to control the new and very lucrative mining operations by reasserting their rights to the large, central farms cum manors. Based on the legal rights in the outfields, which these farms possessed, it was possible to orchestrate the colonisation of the more peripheral land. Thus, we know for instance that the king, Birger Magnusson, in 1303 swapped land with the Swedish Marshal, Torkel Knutsson, for rights in the iron-works near Norberg. Torkel Knutsson was member of the privy council and virtual ruler during the early reign of King Birger Magnusson (1280 -1321).

Whoever was responsible – the nobility, the free peasants or both – it seems obvious than an expansion characterised the 13th century and continued beyond 1300, when the king – for tax-purposes – began to take over by investing heavily in the villages and the more centralised mining operations. This – furthered by the plague – may have led to the gradual desertion of some of the more peripheral settlements post 1350, but the exploitation of iron-ore smelting continued in Bergslagen up until 1920, when most of the smaller forges and foundries, which had survived the competition from the big steel mills, were finally shut down. It has been argued from pollen-analysis and profiles of sediments that the medieval high-water-mark was reached after 1430 – 50. This chronology fits well with other recent studies of an archaeologically documented early smelting site (Moshyttan near the town of Nora). However, already in 1368 osmund iron constituted one third of the exports from Stockholm to Lübeck. Iron was big business for medieval Sweden and probably the foundation on which the kingdom was built.

Medieval Landscapes

The study of these medieval mining landscapes is complicated by a number of facts. First of all, so little written evidence can be found. Moreover, as most localities continued mining up until our time, the surroundings have been literally covered in slags complicating the dating of any remains.

However, from 1978 – 1983 archaeological excavations recovered the remains of a blast furnace and its surrounding homestead at Lapphyttan and Olsbenning in Norberg. This area was not settled until the 12^th century and it is generally believed that the settlement was part of the introduction of proto-industrial mining activities from the same period.

Perhaps of special importance was a hut with a heavily protected door. Here the iron was kept until it might be shipped and sold. Sources indicate that Norberg, to which district Lapphyttan belonged, in whole or part was owned by Tyrgil Knuttson and that the hut was holding his share.

Those who worked at Lapphyttan lived in nearby Olsbenning, located somewhat south where another iron hut could be found. This continued to be inhabited after the plague, while the iron-work at Lapphyttan was deserted.

In 2012 a medieval museum was created in Karlberg (Nya Lapphyttan) with a reconstructed medieval blast furnace built on the remains found at Lapphyttan. The place holds a blast furnace, and an oven for roasting – brittling – the rock, a smithy, a medieval house, stable and other typical houses belonging to the medieval settlement.

Since then, reconstructions on site have been carried out. Thus, in summer 2015 more than 30 kg of iron was produced during the last day of the experiment. The site is also home to other projects in which archaeologists experiment with the medieval decarburization, the process whereby the carbon content is reduced.

Copper at Falun

However, Iron was never the only metal mined in the region for export. Another was copper, which was mined at Falun until 1992. This was a hugely important enterprise. It is thus well known that copper-mining at Stora Kopparberget – the great Copper Mountain – yielded two thirds of the global production of copper in the 17^th century. Yet, for a long time historians and archaeologists have sought to trace the beginning of mining activities at the mountain. Were they Early Medieval as some have thought? Or were they in fact later?

One of the challenges is that later mining activities at Falun continued for such a long period seriously working over any archaeological remains and creating enormous amounts of slag, which ended up filling any imaginable cavity as well as clotting up the riverside and the shores of the surrounding lakes; slag, which has also been demonstrated to disturb the layering of the sediments – geochemical, ecological as well as charcoal.

In view of this it might be thought that studying such layering would yield no results. Nevertheless, three nearby sites sites were recently revisited in a new study in order to try once more to date and evaluate any finds of copper in the lake-sediment profiles. The specific object was to evaluate the received opinion that copper-mining took place already in the early middle ages (5^th to 8^th centuries). Until now this conclusion was based on the increases in charcoal particles, as well as an increase in mining materials in the sediment, dating the beginning of the mining activities to c. AD 700.

In the new study, these conclusions have been shown to be wrong. Yes, deposits of charcoal were significant, but they might as well be explained as evidence of iron-age bog-iron melting in bloomery furnaces. To this must be added the results gathered from recent geochemical investigations at Lake Runn. These studies carried out by Bindler and Rydberg were able to be based on less disturbed lake-sediments. This enabled them to demonstrate a significant an unambiguous evidence of increase in traces of mining activities from AD 1235 to 1245. At the same time, the content of organic matter decreased. This could be shown for lead, sulphur, nickel, zinc and copper. The last metal increased 34-fold inside the ten years from 1235 to 1245. The change in the composition of the sediments at the location, where the Falun River runs into the lake was thus very rapid.

The scientists are careful to note that these results do not exclude minor mining-activities prior to this period. However, the results of the geochemical analysis are clear. Mining of copper in Falun did not take off until mid 13^th century; a conclusion, which by the way differs fundamentally with the official one at the World Heritage Site: Falun

This is of course extremely important as it coincides with the exact time, when the expansion in iron-ore melting could be detected at Norberg. Furthermore it fits well with the first written documentation of copper-mining at Falun, which can be dated to AD 1288. This year, the King of Sweden together with eight bishops witnessed a transfer of an eighth of the copper-mine to the bishop of Vesterås. Somewhat later we learn that the King, the bishop of Vesterås, and the local magnate together with two merchants in Lübeck owned the mountain.

Even though we do not possess much written documentation, it seems as if a remarkable intensification of mining at Falun – in which kings, bishops and foreign merchants were heavily engaged – took place around 1250 – 1300, when a similar intensification of iron-ore smelting can be detected in the wider province and further north.

SOURCES:

Was Moshyttan the earliest iron blast furnace in Sweden? The sediment record as an archeological toolbox
By Erik Myrstener, William Lidberg, Ulf Segerström, Harald Biester, David Damell and Richard Bindler
In: Journal of Archaeological Science: Reports (2016) Volume 5, Pages 35–44

Early medieval origins of iron mining and settlement in central Sweden: multiproxy analysis of sediment and peat records from the Norberg mining district
By Richard Bindler, Ulf Segerström, Ing-Marie Pettersson-Jensen, Anna Berg, Sophia Hansson, Harald Holmström, Karin Olsson and Ingemar Renberg

Revisiting Key Sedimentary Archives Yields Evidence Of A Rapid Onset Of Mining In The Mid-13th Century At The Great Copper Mountain, Falun, Sweden
By R. Bindler and J. Rydberg
In: Archaeometry (2016), Volume 58, Issue 4, August 2016

The reconstructed medieval blast furnace at Nya Lapphyttan in Norberg, Sweden

Bergsbruk och aristokrati : järnhantering, jordbruk och landskap i Norbergs bergslag 800-1580
By Anders Törnqvist.
Series: Meddelande från Kulturgeografiska institutionen, vol 138
Stockholm : Kulturgeografiska institutionen, Stockholms universitet, 2008
ISBN 978-91-7155-702-5

Norberg och järnet. Bergsmännen och den medeltida industrialiseringen
By Ing-Marie Pettersson Jensen
Series: Jernkontorets bergshistoriska skriftserie 46.
Stockholm 2012
ISBN 978-91-977783-4-3.