C anadian M ineral:ogist Vol. 18, pp. 165-171 (1980) cOBALTMINERALS IN THEHALLEFORS AREA, BERGSLAGEN, SWEDEN: NEW OCCURRENCESOF GOSTTBITE'PARACOSTIBITE' NISBITEAND COBALTIANULLMANNITE M.A. ZAKRZEWSKI, E.A.J. BURKE eNp H.W. NUGTEREN*' Institute of Earth Sciences,Free University,De Boelelaan1085' 1801HV Amsterdam,The Netherlands AssrRAcr lagen, a Precambrian metallogenic province' nJrgjtagen is well known for its more than Costibite, paracostibite, nisbite and cobaltian ull' Z,OOOiron deposits and more than 200 base- mannite are found associated for the first time in metal deposits,predominantly of the polymetallic the small Gruv&sen and Gettin Pb Zn{u-Ag de- Ag-Pb--Zn({u) type. The Falun, Sala, Gar- posits, western Bergslagen, central Sweden. A review penberg and Kaveltorp mines are representatlve province is of the Co minerals in the Bergslagen bf ttrere sulfide deposits. Practically all ore given. were probably formed by remobilization They are connected with folded' metamor' from older sulfides by hydrothermal deposits of cobalt of rhyolitic composition solutions during emplacement of late orogenic or phbsed volcanic rocks postorogenic granites. (in Sweden called hiilleflintas whete finely crys- talline, and leptites where more coarse grained). Keywords: costibite, paracostibite, nisbite, cobaltian These rocks and the associatedmetasedimentary ullmannite. cobalt ores, electron-microprobe anal- units were intruded and surrounded by graniter ysis, Bergslagen, Sweden. of at least two generations during the l80G- 2000 Ma Svecofennian folding. The geology of SovrlreRe the Bergslagen province has been summarized (1970) and Grip (1978). A Gruvisen et Geton, deux petits gisements de by Magnusson mined in this region as a Pb-Zn-Cu-Ag situ6s dans le Bergslagen occidental Cobalt ores were (Subde centrale), on trouve pour la premiEre fois by-product of the copper ores. Betweel.lAlZ I'association costibite, paracostibite, nisbite et ull- aira ISOSabout 310 metric tons of metallic Co mannite cobaltifdre. Aprbs r6examen des min6raux were extractedfrom sevenmines (Fig. 1): the de cobalt du Bergslagen, nous proposons comme Gladhammar mine produced 89.6Vo of the total, m6canisme g6n6tigue une remobilisation hydrother- Yena 8.7/o and Tunaberg l.3Va; O.4Vo came pendant en male du Co de sulfures anciens la mise from the HAkansboda, Atvidaberg, Los and place granites post-orog6niques. de tardifs, voire Riddarhyttan mines (Tegengren 1924). Minor Cfraduit Par la R6daction) amounti of Co minerals were also found in several other polymetallic ore deposits. paracostibite, nisbite, ullmannite M ots-clis : costibite, Cobaltite is the main source of Co in all the cobaltifire, minerai de cobalt, analyse !r la mi- mentioned above; it also occurs in small crosonde, Bergslagen. SuEde. mines quantities in the Utii, Brodd and Ingelsby mines' .;Smaltite'chloanthite" ( = skutterudite) is de- INtnooucttoN scribed from Vena and Los, but Welin (1965) showed that the museum specimens from Los within the,framework of a cur- Investigations consist of cobaltite. Linnaeite is noted in Glad' project on the petrology and ore geology rent hammar. where it occurs with cobaltite' car- area of central Sweden (Fig. of the Hlllefors rollite and bravoite. and in Riddarhyttan with discovery of the minerals costibite, 1) led to the cobaltite" skutterudite and several cerium min- paracostibite in the Gruv6sen and and nisbite erals. Glaucodot is known from Hlkansboda in of cobaltian ullmannite in Getdn deposits, and large, perfect crystals that occur with cobaltite two mines are small -Cu-Zn-Pb the Getiin deposit. These in ores. Co-bearing arsenopyrite (7.9 occurrences in western Bergs- Pb--Zn{u-Ag wt. Va Co) has been describ€d from the Los mine (Welin 1965). Safflorite occurs in Tuna- *Present address: U.N.D.P.. B.P. 836. Yaound6, berg. Cameroun. In connection with the presenceof nisbite in 165 Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/18/2/165/3445721/165.pdf by guest on 01 October 2021 166 THE CANADIAN MINERALOGIST Ftc. 1. Geological map of the Hbllefors area, simplifieil after Magnusson (1925) and Sundius (1923), with location of examples of cobalt mineralization. Inset shows the location of cobalt-bearing deposits in central Sweden and situation of the Hiillefors area. (l) Late orogenic and postorogenic granites, (2) Svecofennian synorogenic granites, (3) slates and greywackes, (4) greenstones, (5) leptites and hiille- flintas, (6) limestones and dolomites. the Hiillefors area, it is interesting to note the the Bergslagendistrict. Table I presents a sum- Ni minerals of central Sweden. Breithauptite mary of the ore-mineral paragenesesof these was found in Tunaberg (Odman 1933) with deposits. rammelsbergite, nickeline, pentlandite, cobaltite The Get0n mine (Fig. 2) is situated on a and safflorite, in the Sv[rdsjii Zn-Pb-Cu mine small island 8 km east of Filipstad in the west- with Ag, Bi and Mo minerals, and in Kaveltorp ern flank of the Saxi syncline. A magnetite- in Cu-Pb-Zn ores with Bi, Mo, Ag, Au and bearing skarn was developed between the dolo- As minerals. Gersdorffite occurs in the Los mine, mite and leptite unitb that form the border of a and nickelinein Sala.Pentlandite is the common central limestone dome. The sulfides either oc- mineral in Ni mines, where it occurs with pyr- cur in the magnetite ore or form separatebodies. rhotite and chalcopyrite. A cordierite-gedrite quartzite accompanies the magnetite and sulfide ores in the northern part Co MrNsneuzATroNs rN THq Hilnrrons AnEe of the island. This ore-bearing quartzite, which also occurs in other Bergslagensulfide deposits, The discovery of the CoSbS phases in the can be compared with a similar unit in the Getiin and Gruv&sen mines started a search for Falun mine. Production started in 174O,initially Co minerals in about 80 other base-metal de- for iron and later for Cu, Pb and Ag. During posits in the Hiillefors area. Cobalt minerals were short periods of activity before 1918, about found in only six deposits, in addition to two 50,000 tons of magnetite ore were extracted, other localities (Nordmark and G6sborn) de- along with ores containing 650 tons 'of Pb, 50 scribed by Magnusson (1925). Their locations tons of Cu and 40O kg of Ag. As the dumps are marked on the geologicalmap (Fig. 1). All from the last period of production are relatively these Co mineralizations are small and without rich in sphalerite, it is probable that 3'00-600 any economic value, but they constitute an im- tgns of Zn werc also present in the sulfidic portant phenomenon in discussionsof genesisin ores. Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/18/2/165/3445721/165.pdf by guest on 01 October 2021 COBALT MINERALS FROM HALLEFORS. SWBDEN t67 The Gruv6sen deposit (Fig. 3) is located TABLE1. OBEMINERAL ASSEMBLAGES IN CO-BEARING M1NERALIZATION' HALLEFORSAREA about 4 km east of Get6n in the Saxi syncline, which involves slates, greywackes, greenstones, Mineral 1234567891011 dolomites and limestones surrounded by leptites. 0old The mineralization occurs in the dolomites Si lver +++ Al largentm + flanked by sterile limestones, suggestingthat the Bi smuth +{ + carbonates form a local anticline (Magnusson Antimony Galena +t+ tat f 1925). The anticline is truncated to the south by seleniangalena + a post-Svecofenniangranites (1700 Ma: Welin et +++ ++++ l,lurtzi te al. 1977). Ore was excavated from seven mines Troi l ite +t Pyrrhotite during the sixteenth and seventeenth centuries; Pyri te +++ ++ place l',larc asi te + more recent exploitation took from 1906 Mackinawite +t to 1.9'17,and numerous pits and dumps are still Cubanite t+a Chalcopyri te tt++t ++++ in evidence from this operation. The estimated CovelI i te + Stanni te t+ production was about 500 tons of Pb:Zn:Cu in Acanthite + the proportion 11:9:1. The richest deposit was Hessite i Tetradynite the Ling mine in the central part of the car- Bismuthinite -dome. Molybdenite ++++ bonate Judging by the location of the Arsenopyrite ++t dumps, it is assumed that the central storage 0udmundite a Cobaltite t++t+t point of the ores was close to the northern 0ersdorffi te shaft, the Kung Karla mine. There are two types Costibi te ++ Paracostibi te of ore: (1) massive sphalerite with pyrrhotite, Cobaltianullmannite t chalcopyrite and galena and (2) light-colored Nisbite Breithaupti te diopside skarn with rich disseminationsof chal- Nickeli ne Skutterudite copyrite, molybdenite and native bismuth. saffl ori te The Finnfalls mine is a small excavation 2 Tetrahedrite Pyrargyri te +++ km south of Gruvisen. About 250 tons of Cu Pb-Sb-sulfosal t (1) Bi-sul fosal t ore were produced, of two types: rich Cosali te disseminationsof pyrrhotite and chalcopyrite in Galenobismutite greenstone and (2) disseminations with native l4agnetite n t++ Hematite t + bismuth, molyMenite and chalcopyrite, min- Ilmenite t+ Rutile eralogically very similar to the Gruvlsen mine Goethi te ff (Table galena Cassiterite {} 1). The trace-element contents of scheeli te + and sphalerite from both localities are also very 1. 61gylsen,LBng mine (spec. 12f)i 2. Gruv9sen,Torskeback mine; similar. 3. GruvSsen,Dresfall mine; 4. Getbn,stora silver nine (spec. 56C3); 5. Getiin, Koppar+ Norra minei^6. F'innfallsi 7. Nordnark The Nord iron mine oscurs in the Finnshyt- (Magnusson,1925); 8. Nordminei 9. GHsborn(l'lagnusson, 1925); teberg field, 4 km north of Filipstad. The iron 10. Sikfors; 11..Sundsudden (s. l.laesschalck,pers. com.). ores occur in skarns and leptite rocks surrounded by the Filipstad granite. According to Magnus- son (1925) the ore consistsof magnetite with ered by S. Maesschalck (pers. comm. 1'979). accessory pyrrhotite and pyrite; the most in- The geology of the Sikfors mine resemblesthat teresting feature, however, is the occurrence of of the Finnfalls mine. Cobaltite and skutterudite native bismuth. The latter mineral uras found are associatedwith pyrite, pyrrhotite and chal- in samplds from the dumps, as microscopic in- copyrite, which occur together with quartz, clusions in a Co mineralization containing co- chlorite and calcite in gteenstone and in fine- baltite, cobaltian pyrite, linnaeite--corrollite and grained leptite.