b'FeatureBornite conductivityTable 2.Physical property data for bornite and chalcopyrite.Sample no. Bulk Magnetic EMdensity susceptibility conductivityg/cc SI x 105 S/mBornites B1 4.85 72 300B2 4.61 65 234B3 3.95 34 75B4 3.40 32 55B5 4.50 31 515B6 3.24 14 72B7 4.52 40 850B8 3.48 22 71B9 4.38 41 419Figure 1.Mineral compositions in the Cu-Fe-S system (ternary plot, clockwiseB10 4.08 29 305axes, weight percent proportions Table 1). The Cu minerals are important inChalcopyrites copper exploration as they are major ores and are electrically conductive. The Fe minerals are included as they frequently occur with the copper sulphides,CP1 3.01 50 169and they are electrically conductive too. The native metals, Cu and Fe, usuallyCP2 3.08 63 116occur as disseminations or minor masses in host rocks. Their conductivities areCP3 3.53 42 1003of the order of millions S/m; sulphur is an insulator. This ternary plot maps the mineralic combinations of Cu, Fe, S that are of interest in sulphide exploration.CP4 3.45 24 710This article does not address exploration for the three native elements Cu, Fe, S. CP5 3.33 41 522perspective) Measurement techniques employed in this workCP6 3.12 26 244have been discussed in previous articles; details will not beCP7 3.69 78 1214repeated here Ten bornite samples from Zambia, Mexico, andCP8 4.09 60 4238Victoria were tested for density, magnetic susceptibility, andCP9 4.07 48 5530electromagnetic conductivity The results are presented in Table 2 Measurements on twelve samples of chalcopyrite ores from MtCP10 3.94 42 929Isa (Queensland) and Cobar (New South Wales) are also listed CP11 3.37 51 879CP12 2.94 44 218Discussion Notes: Porosities low, not cited; electromagnetic (inductive) conductivities rounded off; measurements deemed accurate to better than 1%; samples B1, B2 from Buchan, Victoria; The data listed in Table 2 and plotted in Figure 3 (conductivity vsB3, B4 from Mexico; B5-B10 from Zambia; samples CP1-10 from Mt Isa Block, Qld; CP 11,12 density) show a range of moderate conductivities for bornite andfrom Cobar Mineral Field, NSW.The bornite and chalcopyrite mineralisations range from veinlet-disseminated through higher conductivities for chalcopyrite, with each sulphide typesem-massive to massive styles and are hosted by felsics or metasediments. Many of confined to separate groups The two groups show an overallthe samples are textured so the EM conductivities cited here are the maximum values increase in conductivity with density ie as sulphide contentmeasured in an induction coil.increases The scatter of points in each group results from thenot observed) and the low magnetic susceptibilities Hexagonal sulphides textural variety, eg grain size and shape, stringers,pyrrhotite could be present, and not contribute much to the lamellae, dendrites, breccia etc Pyrrhotites conductivitymagnetic susceptibility, but this is unlikely as most terrestrial contributions are regarded as minimal or non-existent aspyrrhotite are intergrowths of the hexagonal and monoclinic attested by visual (binocular) examinations (none seen),varieties (Gould, 1967) The extrapolated bornite trend intersects galvanic microprobing (pyrrhotites very low resistivities werebornites density at ~800 S/m; the chalcopyrite trend suggests ~5500 S/m when extrapolated to chalcopyrites densityIt was difficult to find suitable bornite specimens that are devoid of other sulphides (usually pyrrhotite) so the number of data points is limited. However, it seems reasonable to infer the conductivities, while by no means definitive, are usefully indicative as to the mesoscale conductivities of bornite and chalcopyrite. These can be compared to those for chalcocite, pyrite, pyrrhotite, and graphite in Figure 3.Figure 2.Slightly iridescent bornite tetragonal crystal ~ 10 cm3 volume (left)Some work has been published on single crystal bornite and bornite tarnish (right). Bornite is a coppery red/brown colour when fresh,conductivities (Shuey, 1975). Harvey (1928) found a range of but tarnishes rapidly on exposure - peacock ore with purple and blue hues33350 000 S/m for 16 samples from the Harvard University predominating, finally turning almost black with prolonged exposure. Most bornite occurs in massive dark aggregates which show a distinctive brown- Economic Geology Lab collections. Telkes (1950) measured bronze colour on fresh fractures. samples from Bisbee, Arizona769 S/m; Butte, Montana3226 Source: https://en.wikipedia.org/wiki/File:Bornite-Quartz-135210.jpg / CC BY SAS/m; Sangenbausen, Germany6250 S/m; Silverton, Colorado 3.0 https://commons.wikimedia.org/wiki/File:Mineraly.sk_-_bornit.jpg / CC BY 2.014 286 S/m. Takeno et al (1968) measured low conductivities OCTOBER 2022 PREVIEW 42'