Sjögruvan, which translates in English to the "Lake Mine" has been mined on a minor deposit. The paragenesis is of the Långban type. Operations began as early as 1643, and it was mentioned in official records in 1673 and 1698. It was stated in 1697 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, who operated it mainly due to the rare minerals he discovered there.
During the years 1886-1889, the mine produced 303,000 kg of manganese ore and 85,000 kg of iron ore. The mine was 16 meters deep when it was abandoned. The ores where found in a dolomitic carbonate rock, the iron ore was mainly hematite, and the manganese ore was composed of hausmannite, braunite and rhodonite.
References:- Sundius, N (1923) Grythyttefältets geologi. SGU ser C 312.
- Tegengren, F.R. (1924) Sveriges ädlare malmer och bergverk. SGU ser Ca 17.
- Geijer, P. and Magnusson, N.H. (1944) De mellansvenska järnmalmernas geologi. SGU ser Ca 35.
- Palache, C., Berman, H. & Frondel, C. (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, 7th. edition, Volume I: 640.
- Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 844, 845, 857, 1025, 1030, 1041.
- Moore, P.B. (1970) Mineralogy and Chemistry of Långban-type Deposits in Bergslagen, Sweden. Mineralogical Record: 1: 4.
- Moore, P. B. (1972) Contributions to the mineralogy of Sweden. III. On Igelström's manganese arsenates and antimonates from the Sjö Mine, Grythyttan, Örebro County, Sweden. GFF 94 (3), 423-434.
- Wilke, H-J (1976) Mineralfundstellen in Skandinavien. München.
- Mineralium Deposita: 36(7): 641-657.
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http://www.geonord.org/langban/sjo_eng.htm
56 entries listed. 43 valid minerals. 3 type localities (valid minerals).
