The manganese mine Sjögruvan is situated on the southern shore of the lake Halvtron approximately 5 km SE of Grythyttan in Grythytte parish in Örebro county.
Sjögruvan (eng: the lake mine), which is very small, has been mined on some minor mineralisations. The paragenesis is of Långban type. Sjögruvan, whith operations beginning as early as 1643, was mentioned in official records in 1673 and 1698, and in 1697 it was stated that the mine was 4.5 meters deep, " but the mineralisation is flooded by the lake so it is not possible to use". The mine was mentioned once more during the 18th century, but was abandoned completely until it was reopened by L. J. Igelström in the 1860´s. The mine was operated by Igelström, mostly on account of the rare minerals he discovered there.
During the years 1886-1889, the mine produced 303 000 kg Mn-ore and 85 000 kg Fe-ore. The mine was 16 meter deep when it was abandoned. The ores where found in a dolomitic carbonate rock, the Fe-ore was mainly hematite, and the Mn-ore was composed of hausmannite, braunite and rhodonite. A diamond drilling was carried out in 1938, and the ore was then found to continue deeper, but was too small to mine.
Lars Johan Igelström
In the literature there are lots of strange mineral names described from Sjögruvan. Most of these where found, analysed and named by Lars Johan Igelström in late 19th century, when he was mining Sjögruvan (1886-1889). Igelström was a skilled and devoted mineralogist. During the later part of his life he lived on a remote farm in the region of Sunnemo in Värmland, and there in his home he carried out most of his chemical analyses under primitive conditions.
Several of the minerals named by him have in later investigations proved to be already known minerals or mixtures of known minerals. Professor Paul B. Moore investigated some of these during his extensive work on Långban minerals in the Swedish Museum of Natural History in 1970. The result of this reinvestigation is shown in the table below.
|Mineral names by Igelström||Moore's analysis results|
|Basiliite||Hausmannite + feitknechtite|
|Neotostibian||Hausmannite + feitknechitite|
Other minerals named by Igelström as xanthoarsenite, polyarsenite, stibiatile, epigenite, neotesite, chondrostibian, elfstorpite are not accepted today.
Minerals known from Sjögruvan
ANDRADITE, dark brown
BIOTITE, brownish black
BUSTAMITE, brownish red
KARYINITE, brownish red
CERUSSITE, greyish white
DIOPSIDE, dark green
FEITKNECHTITE, brownish black
HAUSMANNITE, greyish black
HEDYPHANE, greyish white
HEMATITE, steel grey
KUTNOHORITE, light red
LEAD, lead grey
MANGANBERZELIITE, reddish yellow
MELANOSTIBITE, black, easy to confuse with hematite; very rare
PIEMONTITE, brownish red
PYROCHROITE, white, darkening very fast in air
RICHTERITE, yellowish green
"SCHEFFERITE" (=ÄGIRINE), brown
SERPENTINE (mineral group), greenish yellow
SPHALERITE, brownish black
TALC, greyish green
TREMOLITE, greyish green
The BGS mineral society's mine description, (BGS 142 (1979) IJ et al) has been the main reference for this compilation.
N: Grythyttefältets geologi. SGU ser C 312 (1923).
Tegengren, FR: Sveriges ädlare malmer och bergverk. SGU ser Ca 17 (1924).
Geijer, P och Magnusson, NH: De mellansvenska järnmalmernas geologi. SGU ser Ca 35 (1944).
Wilke, H-J: Mineralfundstellen in Skandinavien. München, 1976.
Moore, PB: Mineralogy and Chemistry of Långban-type Deposits in Bergslagen, Sweden. Min Rec 1(1970):4.