Jakobsberg

 

            Location

 

                The Jakobsberg manganese mines are situated about one km south of the church in Nordmark, Värmland County.

 

                Nordmark mining district – schematic map

 

Map modified from original at www.filipstadsbergslag.com

 

1.                       Taberg canal

2.                       Taberg mines                                             

3.                       F. A. Dahlgren monument

4.                       Limkullen limestone quarry

5.                       Mining museum

6.                       Gun powder stores

7.                       Taberg water wheel (11 m diameter)

8.                       Smelting-works ruins

9.                       Church

10.                    Nordmarksberg mines

11.                    Värmlandsberg mine

12.                    Jakobsberg mines

13.                    Finnmossen mines

 

          History of the Mine

 

The Jakobsberg ore field embraces three mines, of which only the northernmost has been of economic importance.

The deposit was discovered in 1863 by the ore prospector and mine manager Lars Johan Igelström. Soon after the discovery the largest company in the area, Uddeholmsbolaget, bought 25% of Jakobsberg. The company needed manganese ore for use in their blast furnaces, and the Jakobsberg ore held 53.53% MnO. The ore used previously was from Skarinna in the Björnberg field, Nordmark, and had a MnO content of approx. 5%. Hausmanite ore from Jakobsberg was sold by Igelström at 55 öre per center (1 center =42.5 kg, 55 öre = $0,07).

However, before that time, the mine had probably been in operation on and off since 1694 under the name of “Gräsåsskärpningarna”. The target then was the iron ore, said to be “good, but hard-mined”. Gräsåsskärpningarna are also mentioned in different papers from 1706, 1733 and 1793, but all reports indicate poor mining results.

Several limestone quarries are also found in the surrounding dolomitic marble, all of them from the time before Igelström’s discovery.

Igelström began working at Jakobsberg in 1864, and in 1871 he reports that two smaller mines are being worked for hausmanite and braunite (as a matter of fact, Jakobsberg was the first Swedish braunite locality). The ore body seems to have been small, though, as Igelström appreciated the value of the whole mine to be 800 riskdaler in 1872 (printed in the annual report of the Uddeholm Company that year).

 

After some years of abandonment the mine was reopened in 1886, but soon closed again due to lack of both iron and manganese ore. That same year the small mine to the south was also worked. This ore was mined again in 1891, when 200 tons of manganese ore and 200 tons of “manganese marble” were taken out. In 1898 two men were occupied in the mine, and the yield was 125 tons of manganese ore out of 400 tons of mined rock. The ore was said to be good, but contained some native copper. During World war I the import of manganese ore to Sweden was heavily obstructed, and Uddeholm decided to investigate the Jakobsberg occurrence once more. The mine was free from water by the end of 1917. Mining and investigation by diamond drilling was carried out at a cost of more that SEK 20.000 (approx. $2500). 2779 tons of rock were mined until October 1918, after which the mine was closed down. The old mine (the northernmost) was then about 27 m deep, and no further ore could be detected. Out of the 2779 tons mined only 27.9 tons of primary and 17.27 tons of secondary manganese ore were recovered, together with 131.62 tons of “manganese marble”.

 

In order to explore if more ore was present, two drilling holes with a total length of 71 m were drilled in early 1919. The result was negative, and no ore was encountered below the bottom level of the old mine.

 

The total amount of manganese ore mined in Jakobsberg equalled 380 tons.

 

Paragenetically the Jakobsberg ore mineralization is of the Långban type, and the ores where hosted in a carbonate rich (dolomitic) rock. The Fe-ore was mainly hematite with minor magnetite, and the Mn-ore was a complex of hausmanite, jakobsite and braunite.

 

Minerals:

 

More than 100 different minerals have been reported from Jakobsberg. Six of them are type minerals, e.g. jakobsite, named after the locality. The most recently described type mineral is lindquistite (1992).

 

A             Adelite, actinolite, andalusite, andradite, antigorite, azurite

 

B             Barylite, barysilite, barite, berzeliite, bindhemite, braunite, brucite

 

C             Calcite, celsian, cerussite, chalcocite, chalcopyrite, copper, cordierite, covellite, crednerite, cuprite

 

D             Digenite, diopside, dolomite, (alpha-)domeykite

 

E             Ecdemite, epidote, ericssonite

 

F              Feitknechtite, phenakite, ferro-actinolite, ferrohornblende, filipstadite, fluorite, fredrikssonite

 

G             Gahnite, galaxite, galena, ganomalite, glaucochroite

 

 

 

                           

                Johnbaumite.   Photo: F.Sandström                                            Margarosanite.   Photo: F. Sandström

 

 

H             Hancockite, hausmanite, hedyphane, heliophyllite, hematite, hematophanite, hisingerite, hyalophane

 

I              Inesite, iwakiite

 

J              Jakobsite, johnbaumite

 

K             Katoptrite, kentrolite

 

L             Lead, lindquistite, lithargite

 

M            Macedonite, magnetite, magnetoplumbite, malachite, manganosite, manganostibite,

manganvesuvianite, margarosanite, melanotekite, microcline, mimetite, molybdenite, molybdophyllite, morelandite, muscovite

 

N             Nadorite, nasonite, neotocite

 

P              Paracelsian, paulmooreite, pectolite, periclase, phlogopite, picrotephroite, piemontite, plumboferrite,

                prehnite, pyrite, pyroaurite, pyrochroite, pyrolusite, pyrophanite, pyrophyllite

 

R             Richterite, rhodonite, romeite, rutile

 

S              Sahlinite, sanidine, scapolite, schefferite, sillimanite, sjögrenite, spessartine, sphalerite, svabite

 

T             Talc, tephroite, tilasite, titanite, tremolite, trimerite

 

V             Vesuvianite

 

W            Wenkite, wollastonite

 

 

Cymrite, calcite.   Photo: F.Sandström

 

 

Domeykite.   Photo: F.Sandström

 

 

 

Melanotekite. SEM photo by K. Gatedal

 

 

Ericssonite (orthoericssonite). Photo: K. Gatedal

 

 

                                                                                                        Macedonite (polished section), with zircon crystal inclusion. The white lists are barysillite. Photo: K Gatedal

 

Manganostibite (polished section). Photo: K. Gatedal

 

 

Literature:

 

1                     Carlborg, H: Världens manganmalmstillgångar. Jernkontorets Annaler 84(1929):4, 135-181

2                     Magnusson, Nils H: Nordmarks malmtrakt. Geologisk beskrivning. SGU ser A nr 13(1929)

3                     Moore, P B: Mineralogy & Chemistry of Långban-type Deposits in Bergslagen, Sweden. Min Record (1971) 154-172

4                     Igelström, L.J.: Sällsynta och nya mineralier från Vermland: manganepidot, richterit eller manganhornblende, kataspilit och hyalophan. Öfversigt af Kongl. Vetenskaps-Akademiens Förhandlingar 24(1867) 11-18

5                     Igelström, L.J.: Plumboferrit, ett nytt mineral från Jakobsbergs manganmalmsgrufva vid Nordmarken i Wermland. Öfversigt af Kongl. Vetenskaps-Akademiens Förhandlingar 38(1881) 27-31

6                     Holtstam, D. Norrestam, R.: Lindqvistite, Pb2MeFe16O27, a novel hexagonal ferrite mineral from Jakobsberg, Filipstad, Sweden. American Mineralogist 78(1993) 1304-1312

7                     Holtstam, D. Langhof, J.: Hancockite from Jacobsberg, Filipstad, Sweden: the second world occurrence. Mineralogical Magazine 58(1994) 172-174 

8                     LapId – svensk mineralencyklopedi för PC ver. 2

9                     SMIDA, Svensk Mineral Databas v 3.1 (1988). U Strand et al

10                 Fyndortsbeskrivning Nr 3 – Jakobsberg (1989) Dan Johansson & Gun Bergquist, Geologiska Föreningen i Göteborg [Field guide to Jakobsberg]