b'FeatureBornite conductivityFigure 3.Cross plot of EM conductivity against bulk density for suites of bornites and chalcopyrite measured (Table 2) at mesoscale. Ranges of microscale single crystal data are included for comparison: Hvy (Harvey, 1928) 16 measurements from unspecified localities; Tlk (Telkes, 1950) four localities; and Tak (Takeno et. al., 1968) nominal measurement; all measured by microgalvanic techniques and cited by Shuey (1975). Nominal values for massive deposits of graphite (gr), pyrrhotite (po), chalcopyrite (cpy), pyrite (py), and chalcocite (cc) are also plottedthese values are based on previous work. The data plot suggests that materials regarded in the field as bornite are less conductive than chalcopyrite, and intermediate between pyrite and chalcocite, ~800 S/m for 100% bornite. Note that the single crystal conductivities of the reference minerals [graphite, pyrrhotite, covellite (cv), digenite(dg)] can be much higher than the massive mineral aggregate values plotted here.~13 S/m, for natural and synthetic bornites These values(e.g see my article on Broken Hill galena ore, Preview 188) are plotted on Figure 3, where it is seen that Harveys lowestPyrite, in aggregated grains and crystals, is not so conductive conductivity and Telkes Bisbee sample conductivity are similarThe three major sulphide ores of copper, if pyrrhotite-free, to that extrapolated to the massive bornite ore density Mostare moderately to highly conductive: bornite - chalcocite - of the single crystal bornite conductivities have higher or farchalcopyrite More bornite measurements would be desirable higher values than those measured in this study; the Takenoeither to corroborate or modify these conclusions The effects, etal. value is far lower Shuey (1975) suggests that the lowif any, of other copper sulphides (such as covellite and digenite) Takeno conductivity may be appropriate for bornite and thaton commercial Cu sulphide ores need further investigationvery fine included networks of extremely conductive digenite and covellite are responsible for the higher conductivitiesAcknowledgementsThese minerals have been apparently observed by others at highest magnification in optical studies of some bornitesThanks are due to David Kalnins for suggestions, and for the Be that as it may, and noting that such considerations andpreparation of the manuscript and figuresdetail are far beyond the scope of this preliminary study, it is clear that this studys multicrystalline bornite samples fromReferencesthree localities manifest conductivities intermediate betweenArnold, RG, 1967 Range in composition and structure of 82 chalcopyrite and pyrite and probably below that of chalcocitenatural terrestrial pyrrhotites: Canad. Mineral., 9, 31-50These conductivities are considered to be of the order of severalHarvey, RD, 1928 Electrical conductivity and polished mineral hundred S/m for massive bornite sulphides If Takeno etal. aresurfaces, Economic Geology and the Bulletin of the Society of to be believed, the bornites may have incorporated threadedEconomic Geologists, 23, 778-803networks of minor or trace amounts of more conductive copperKlein, C, & Hurlbut, CS, 1993 Manual of Mineralogy (after sulphides, but it was not possible to establish or refute thatJ.D.Dana): John Wiley & Sonspossibility here Shuey, RT, 1975 Semiconducting ore minerals, ElsevierConclusions Takeno, S, Masumoto, K, and Kamigachi, 1968 Electric and magnetic properties of bornite: J. Sci. Hiroshima Uni. C5, 321-332In articles over recent years, I have provided data on theTelkes, M, 1950 Thermoelectric power and electrical resistivity mesoscale conductivities of several members of the importantof minerals, American Mineralogist, 35, 536-555Cu-Fe-S system: previously pyrite, pyrrhotite, chalcocite; nowDon Emerson is a geophysical consultant specialising in bornite and chalcopyrite The data and analyses suggest thatthe physics of minerals and rocks, he also has an interest in pyrrhotite is extremely conductive and its pervasive habit willancient and medieval geoscience dominate conductivity in sulphide ores, even in small amounts 43 PREVIEW OCTOBER 2022'