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Håkansboda, Lindesberg, Örebro, Sweden

The name Håkansboda combines a variety of different mines (at least eight). Mining started as early as 1400 and continued with interruptions until 1982. Carlon (1986) summarized the geological situation: „In summary, the stratigraphy displays a change from a volcanic dominated depositional environment, with sodic to potassic rhyolitic-rhyodacitic volcanism, into a mixed carbonate-clastic-chemical sediment, possible shallow sea-water environment. Volcanic detritus forms fine grained 'tuffs' {hälleflinta) together with carbonate, calcareous, argillaceous and ferruginous sediments. Into this environment, it is proposed, a sub-seafloor hydrothermal system developed, producing massive sulphide deposition and rock alteration.“ And for the mineralogy he mentions two different associations: „A main chalcopyrite-pyrrhotite-arsenopyrite-pyrite mineralization with subordinate magnetite, molybdenite, tennantite and cobaltite. This characterizes the zone of mineralization and constitutes the major part of the more massive ‚ore-shoots‘.“ and „A superimposed galena-tetrahedrite-tennantite native bismuth-gold mineralization.“ The shown sample is from the first association.

A polished slab of the ore, containing pyrrhotite, chalcopyrite and cobaltite:

Hakansboda_104

A 6400 dpi scan covering about 20 mm of the sample:

Hakansboda_205

The polished sample was prepared from a very cobaltite rich ore specimen. Foto with Nic //, Obj. 20x, air, 100 µm scale bar. Euhedral cobaltite (Cbt), chalcopyrite (Ccp) and cubanite (Cub):

Hakans

Same with Nic +:

image_410_920_0000306

Same with Nic +, 90° rotated:

image_410_920_0000405

Euhedral cobaltite (Nic //, Obj. 20x, air, 100 µm scale bar):

image_410_920_0000704

Euhedral cobaltite, chalcopyrite and pyrrhotite (Nic //, Obj. 20x, air, 100 µm scale bar):

image_410_920_0000803

Cobaltite (Cbt), chalcopyrite (Ccp) and pyrrhotite (Po): Nic //, Obj. 20x, air, 100 µm scale bar:

Hakans2

Cobaltite (Cbt), pyrrhotite (Po) and pyrite (Pyr); Nic //, Obj. 20x, air, 100 µm scale bar:

Hakans3

For further informations on the region these articles might be interesting:

Bäckström (2007): Översiktlig geokemisk undersökning av gruvavfall vid Håkansbodafältet, Lindesbergs kommun

Carlon, Chris J. (1986): Report No: B 86-7, Project 3822 HAKANSBODA, Mineralization in the Håkansboda area. Its geology, exploitation, exploration and potential. (Annual Report and Project Background 1985). Geological Survey of Sweden