"Rock of the Month #184, posted for October 2016" ---

Breithauptite

is an ore mineral seldom encountered in hand specimen, or indeed under the microscope. The ideal formula is a simple antimonide, NiSb, corresponding to 32.5 wt.% Ni and 67.5 wt.% Sb. This dense, lustrous ore mineral may incorporate lesser amounts of other valuable elements into its crystal lattice, an example being palladium (Cabri, 1992). This mineral is very dense (specific gravity of pure material circa 8.23), and though the crystal symmetry is hexagonal, the material most often appears massive to reniform in hand specimen.

Occurrence

Discovery of rich silver veins in the Cobalt district of Ontario led to a long history of continuous silver production from 1903 to 1989. Research on the ores gave rise to descriptions of veins of unusually complex mineralogy and ore textures (e.g., Miller, 1913; Bastin, 1917: see also "Rock of the Month 40, arsenide ore"). The mineral listing includes, besides native silver, native bismuth and a horder of other minerals, such as sulphides and sulphosalts, arsenides and antimonides. The ore minerals include smaltite, niccolite, breithauptite and chloanthite, erythrite and other secondary salts, cobaltite, arsenopyrite, dyscrasite and pyrargyrite. The gangue (waste) minerals are dominated by calcite and dolomite. The Cobalt-Gowganda area is noted for complex Ag ores with diverse Ni- Co- As- Sb- S mineral species (Petruk et al., 1971). Notable minerals include niccolite (nickeline, NiAs, with up to 6.5 wt.% Sb, 3.9% Co and 0.7% Fe), diarsenides such as safflorite, which is the most common arsenide in the ores of the region, and triarsenides such as skutterudite, which is found in all the arsenide assemblages. A valuable, recent compilation, with illustrations of fine specimens, is given by Joyce et al. (2012), and much of the material is in the collections of the Royal Ontario Museum in Toronto.

Breithauptite is reported as a minor component of a number of ore deposits, which contain variable proportions of silver, gold and base metals. These include Ni-Cu-PGE deposits, sediment-hosted base-metal and manganese deposits, and even a large alkaline igneous complex. A new treasury of ore mineral species and textures, including many examples from Argentina, includes niccolite and breithauptite (Paar et al., 2016). The mineral appears in a number of reviews of localities (e.g., Bernard and Hyrsl, 2015). A partial listing of occurrences is as follows:

• Sulitjelma, Norway
• Bergslagen, Sweden
• Vammala, Finland
• The Shetland ophiolites, northern Scotland
• Leadhills district, Southern Uplands, Scotland (Chapman et al., 2000)
• Andreasberg, Harz, Germany
• El Molar deposit, Spain
• Sarrabus, Sardinia, Italy
• Ilimaussaq complex, southwest Greenland
• Wellgreen deposit, Yukon, Canada
• Tulameen district, British Columbia, Canada
• MacLellan gold deposit, Lynn Lake, Manitoba, Canada
• Cobalt silver camp, Ontario, Canada
• Raglan belt, northern Quebec, Canada
• Voisey's Bay deposit, Labrador, Canada
• Aguilar mine, Jujuy, Argentina
• Rajasthan, northwest India
• Kolar gold field, south India

Some unusual hydrothermal occurrences are also reported. Ore minerals (in the normal heavy-metal context) are rare in the Ilimaussaq peralkaline intrusion, in the Gardar province along the western coast of south Greenland. Arsenides and antimonides are part of a late, relatively low-temperature paragenesis, including galena, skutterudite, breithauptite, niccolite, maucherite, loellingite and gudmundite (Soen and Sorensen, 1964). More typical are remobilizations of existing metallic ores. At the Sulitjelma massive sulphide deposit in Norway, two Au and Sb mineral parageneses occur in coarse segregations related to late remobilization of part of the sulphide mass. The associations, deposited from S-poor fluids at <300°C, are (a) galena, freibergite, gudmundite, aurostibite and electrum, and (b) breithauptite, gudmundite, electrum, galena and pyrrhotite (Cook, 1992). At the large, metamorphosed Rampura-Agucha sedex Pb-Zn deposit in Rajasthan, rare minerals include native Sb and breithauptite (Gandhi, 2003: Pal and Deb, 2009). NiSb is one of a number of Ni-Sb-Te minerals that form under specific conditions at relatively low temperatures (Laufek et al., 2010).

Breithauptite is often found with base-metal sulphides such as galena (PbS), with arsenides and silver minerals. It seems to be most abundant in veins and other concentrations of remobilized sulphides. Such remobilization may be induced by regional metamorphism, or by sequential intrusion of batches of magma. The resulting hydrothesrmal assemblages evidently form at modest temperatures, <450°C to <300°C.

Historical Notes

The Freiberg Mining Academy began supplying students with mineral specimens in 1765 (Wilson and Neumeier, 2015). Famous geoscientists who worked there include Abraham Gottlob Werner, Wilhelm Maucher, and the man in whose honour breithauptite was named, Johann Friedrich August Breithaupt (1791-1873). Breithaupt was a mineralogist and a professor at the Freiberg Mining Academy in Saxony. He studied under Werner and succeeded Mohs as professor of mineralogy. He is credited with the discovery of 47 valid mineral species, and with the development of the concept of paragenesis (the chronological evolution of mineral assemblages, especially in ore deposits). The modern breadth of the Freiberg Mineralogical Collection is very impressive.

Technical Note

NiSb is an electrical conductor, somewhat like native metals (copper, silver, iron...) and the ferrosilicon class of industrial alloys. The good electrical conductivity (σ, measured in Siemens/m) in these minerals and alloys defeats simple measurement of bulk magnetic susceptibility using a coil-based meter like the SM-30 (the apparent, erroneous, answer, as with ferrosilicon or native copper, is always a large negative number). Metals, and graphite (parallel to cleavage planes) are good conductors, with low electrical resistivity, whereas typical ore minerals (common sulphides) are not. As a bonus, minerals such as copper, silver and breithauptite, as well as iron meteorites, may all be found using metal detectors. Approximate resistivity values (ρ, the inverse of conductivity, and measured in ohm-metres) for a few metals and other ore minerals (Keller, 1987) are as follows:

References, in Chronological Order

Miller,WG (1913) The cobalt-nickel arsenides and silver deposits of Temiskaming (Cobalt and adjacent areas). OBM Ann.Rep. 19 part 2, 4th edition, 279pp.

Bastin,ES (1917) Significant mineralogical relations in silver ores of Cobalt, Ontario. Econ.Geol. 12, 219-236.

Soen,OI and Sorensen,H (1964) The occurrence of nickel-arsenides and nickel-antimonide at Igdlunguaq, in the Ilimaussaq alkaline massif, South Greenland. GGU Bull. 43, 50pp.

Petruk,W, Harris,DC and Stewart,JM (1971) Characteristics of the arsenides, sulpharsenides, and antimonides. In `The Silver-Arsenide Deposits of the Cobalt-Gowganda Region, Ontario' (Petruk,W and Jambor,JL compilers), Can.Mineral. 11 Part 1, 429pp., 150-186.

Keller,GV (1987) Rock and mineral properties. In `Electromagnetic Methods in Applied Geophysics - Theory. Volume 1' (Nabighian,MN editor), 513pp., Chapter 2, pp.13-52, Society of Exploration Geophysicists, Tulsa, OK.

Cabri,LJ (1992) The distribution of trace precious metals in minerals and mineral products. Mineral.Mag. 56, 289-308.

Cook,NJ (1992) Antimony-rich mineral parageneses and their association with Au minerals within massive sulfide deposits at Sulitjelma, Norway. NJMM 1992 no.3, 97-106.

Chapman,RJ, Leake,RC, Moles,NR, Earls,G, Cooper,C, Harrington,K and Berzins,R (2000) The application of microchemical analysis of alluvial gold grains to the understanding of complex local and regional gold mineralization: a case study in the Irish and Scottish Caledonides. Econ.Geol. 95, 1753-1773.

Gandhi,SM (2003) Rampura-Agucha Zinc-Lead Deposit. Geol.Soc.India Memoir 55, 154pp.

Pal,T and Deb,M (2009) Breithauptite: a rare antimonide in the Dariba-Rajpura-Bethumni belt, Rajsamand district, Rajasthan. J.Geol.Soc.India 74, 35-38.

Laufek,F, Drabek,M and Skala,R (2010) The system Ni-Sb-Te at 400°C. Can.Mineral. 48, 1069-1079.

Joyce,DK, Tait,KT, Vertolli,V, Back,ME and Nicklin,I (2012) The Cobalt mining district, Cobalt, Ontario, Canada. Mineral.Record 43, 685-713.

Bernard,JH and Hyrsl,J (2015) Minerals and their Localities. Granite, Prague, Czech Republic / Mineralogical Record Bookstore, Tucson, 3rd edition, 920pp., p.106.

Wilson,WE and Neumeier,G (2015) The mineral dealership of the Freiberg Mining Academy. Mineral.Record 46, 395-409.

Paar,WH, de Brodtkorb,MK, Putz,H and Martin,RF (2016) An Atlas of Ore Minerals: Focus on Epithermal Deposits of Argentina. Mineral.Assoc.Canada Spec.Publ. 11, v+402pp. plus DVD-ROM, pp.133,221.