OREAS 282b

OREAS 282b was prepared from a blend of gold ores and barren materials comprising quartz, black slate, pyrite, white marble, dolomite, and graphite. The ores were sourced from both the Leeville and Deep Post Mines, located near the western crest of the Tuscarora Mountains, approximately 20 miles northwest of Carlin, Nevada, USA. Both mines are underground, high-grade refractory gold deposits on the Carlin Trend. The ores were provided by Nevada Gold Mines, operated under Barrick’s management. The deposits are hosted in carbonate rocks within the Carlin Trend, where gold occurs as fine-grained, disseminated, and structurally controlled Carlin-type mineralisation, commonly associated with pyrite and arsenian pyrite in decalcified and weakly to moderately silicified zones.

The ores are double-refractory, containing both sulphidic sulphur and carbonaceous (organic) matter. Gold occurs as submicroscopic inclusions within sulphide minerals and is also adsorbed onto organic carbon surfaces, which can exhibit strong preg-robbing behaviour during cyanidation.

Fifty-nine commercial analytical laboratories participated in the program to certify the elements reported below using the following methods:

  • Gold by Pb collection fire assay (25-50g charge weight) with AAS and ICP-OES finish
  • Gold by Bi collection fire assay (30 g charge weight) with AAS finish
  • Gold by PhotonAssay™ (protocol PAAU02) with recommended gross fill mass of 445-475 g
  • Total C and S by IR combustion furnace
  • Full ICP-OES and ICP-MS elemental suites by 4-acid (HNO3-HF-HClO4-HCl) digestion
  • Full ICP-OES and ICP-MS elemental suites by aqua regia digestion

To confirm homogeneity, gold by instrumental neutron activation analysis (INAA) was undertaken on 20 x 85mg. This format enabled a nested ANOVA treatment of the INAA results to compare within- and between-unit variances, providing a statistical measure of batch homogeneity.

Analyte Certified Value 1SD Expanded Uncertainty Low Expanded Uncertainty High Method
Au, Gold (ppm) 15.02 0.424 14.90 15.14 Pb Fire Assay
Au, Gold (ppm) 15.17 0.281 Bi Fire Assay
Au, Gold (ppm) 15.36 0.271 15.27 15.45 PhotonAssay
C, Carbon (wt.%) 2.00 0.046 1.97 2.04 Infrared Combustion
S, Sulphur (wt.%) 2.23 0.066 2.18 2.28 Infrared Combustion
Ag, Silver (ppm) 2.35 0.190 2.21 2.49 4-Acid Digestion
Al, Aluminium (wt.%) 3.24 0.089 3.15 3.33 4-Acid Digestion
As, Arsenic (wt.%) 0.507 0.025 0.490 0.523 4-Acid Digestion
Be, Beryllium (ppm) 0.77 0.050 0.70 0.83 4-Acid Digestion
Bi, Bismuth (ppm) 0.33 0.019 0.31 0.35 4-Acid Digestion
Ca, Calcium (wt.%) 3.15 0.101 3.06 3.25 4-Acid Digestion
Cd, Cadmium (ppm) 1.85 0.112 1.74 1.96 4-Acid Digestion
Ce, Cerium (ppm) 38.1 1.72 36.3 39.8 4-Acid Digestion
Co, Cobalt (ppm) 6.47 0.484 6.09 6.85 4-Acid Digestion
Cr, Chromium (ppm) 54 6 49 58 4-Acid Digestion
Cs, Caesium (ppm) 6.22 0.238 5.91 6.54 4-Acid Digestion
Cu, Copper (ppm) 33.3 1.97 31.2 35.4 4-Acid Digestion
Dy, Dysprosium (ppm) 2.20 0.145 2.04 2.36 4-Acid Digestion
Er, Erbium (ppm) 1.21 0.114 1.10 1.32 4-Acid Digestion
Eu, Europium (ppm) 0.75 0.12 0.63 0.87 4-Acid Digestion
Fe, Iron (wt.%) 2.44 0.078 2.38 2.51 4-Acid Digestion
Ga, Gallium (ppm) 8.60 0.320 8.18 9.01 4-Acid Digestion
Gd, Gadolinium (ppm) 2.72 0.151 2.54 2.89 4-Acid Digestion
Hf, Hafnium (ppm) 1.44 0.091 1.31 1.56 4-Acid Digestion
Ho, Holmium (ppm) 0.42 0.015 0.39 0.45 4-Acid Digestion
In, Indium (ppm) 0.052 0.007 0.044 0.061 4-Acid Digestion
K, Potassium (wt.%) 1.11 0.039 1.07 1.15 4-Acid Digestion
La, Lanthanum (ppm) 21.7 1.22 20.5 22.9 4-Acid Digestion
Li, Lithium (ppm) 32.5 1.50 31.3 33.7 4-Acid Digestion
Lu, Lutetium (ppm) 0.16 0.010 0.15 0.18 4-Acid Digestion
Mg, Magnesium (wt.%) 0.919 0.024 0.891 0.946 4-Acid Digestion
Mn, Manganese (wt.%) 0.016 0.000 0.015 0.016 4-Acid Digestion
Mo, Molybdenum (ppm) 21.4 0.76 20.5 22.3 4-Acid Digestion
Na, Sodium (wt.%) 0.031 0.004 0.028 0.033 4-Acid Digestion
Nb, Niobium (ppm) 8.59 0.533 8.09 9.09 4-Acid Digestion
Nd, Neodymium (ppm) 18.0 0.49 16.9 19.1 4-Acid Digestion
Ni, Nickel (ppm) 41.4 1.87 39.6 43.1 4-Acid Digestion
P, Phosphorus (wt.%) 0.058 0.002 0.057 0.060 4-Acid Digestion
Pb, Lead (ppm) 18.2 1.01 17.1 19.3 4-Acid Digestion
Pr, Praseodymium (ppm) 4.84 0.204 4.60 5.07 4-Acid Digestion
Rb, Rubidium (ppm) 60 3.0 57 63 4-Acid Digestion
Re, Rhenium (ppm) 0.029 0.003 0.025 0.033 4-Acid Digestion
S, Sulphur (wt.%) 2.19 0.060 2.13 2.24 4-Acid Digestion
Sb, Antimony (ppm) 167 6 161 174 4-Acid Digestion
Sc, Scandium (ppm) 4.76 0.200 4.54 4.98 4-Acid Digestion
Se, Selenium (ppm) 2.41 0.46 1.85 2.97 4-Acid Digestion
Sm, Samarium (ppm) 3.22 0.124 3.07 3.38 4-Acid Digestion
Sn, Tin (ppm) 2.37 0.157 2.18 2.56 4-Acid Digestion
Sr, Strontium (ppm) 47.8 2.12 45.7 49.8 4-Acid Digestion
Ta, Tantalum (ppm) 0.41 0.06 0.36 0.45 4-Acid Digestion
Tb, Terbium (ppm) 0.38 0.028 0.35 0.41 4-Acid Digestion
Te, Tellurium (ppm) 1.94 0.148 1.81 2.07 4-Acid Digestion
Th, Thorium (ppm) 5.25 0.459 4.91 5.58 4-Acid Digestion
Ti, Titanium (wt.%) 0.169 0.009 0.162 0.177 4-Acid Digestion
Tl, Thallium (ppm) 45.6 3.15 43.3 47.9 4-Acid Digestion
Tm, Thulium (ppm) 0.16 0.014 0.13 0.18 4-Acid Digestion
U, Uranium (ppm) 5.07 0.255 4.81 5.32 4-Acid Digestion
V, Vanadium (ppm) 186 9 178 193 4-Acid Digestion
W, Tungsten (ppm) 63 2.6 60 66 4-Acid Digestion
Y, Yttrium (ppm) 13.5 0.74 12.9 14.2 4-Acid Digestion
Yb, Ytterbium (ppm) 1.08 0.041 1.00 1.16 4-Acid Digestion
Zn, Zinc (ppm) 170 7 165 175 4-Acid Digestion
Zr, Zirconium (ppm) 49.9 3.14 47.5 52.4 4-Acid Digestion
Ag, Silver (ppm) 2.32 0.157 2.21 2.44 Aqua Regia Digestion
Al, Aluminium (wt.%) 0.684 0.060 0.644 0.725 Aqua Regia Digestion
As, Arsenic (wt.%) 0.500 0.020 0.487 0.514 Aqua Regia Digestion
Au, Gold (ppm) 5.52 0.60 4.97 6.08 Aqua Regia Digestion
Be, Beryllium (ppm) 0.29 0.03 0.25 0.33 Aqua Regia Digestion
Bi, Bismuth (ppm) 0.30 0.020 0.28 0.32 Aqua Regia Digestion
Ca, Calcium (wt.%) 3.10 0.157 2.99 3.21 Aqua Regia Digestion
Cd, Cadmium (ppm) 1.85 0.094 1.74 1.95 Aqua Regia Digestion
Ce, Cerium (ppm) 22.8 1.29 21.8 23.8 Aqua Regia Digestion
Co, Cobalt (ppm) 6.38 0.308 6.11 6.64 Aqua Regia Digestion
Cr, Chromium (ppm) 25.6 1.89 24.4 26.9 Aqua Regia Digestion
Cs, Caesium (ppm) 2.74 0.267 2.57 2.91 Aqua Regia Digestion
Cu, Copper (ppm) 32.4 1.57 30.7 34.1 Aqua Regia Digestion
Fe, Iron (wt.%) 2.37 0.082 2.30 2.44 Aqua Regia Digestion
Ga, Gallium (ppm) 2.17 0.23 1.99 2.36 Aqua Regia Digestion
Hf, Hafnium (ppm) 0.17 0.02 0.15 0.18 Aqua Regia Digestion
Hg, Mercury (ppm) 34.5 2.18 32.8 36.2 Aqua Regia Digestion
In, Indium (ppm) 0.045 0.004 0.041 0.049 Aqua Regia Digestion
K, Potassium (wt.%) 0.247 0.018 0.234 0.260 Aqua Regia Digestion
La, Lanthanum (ppm) 12.2 0.70 11.7 12.7 Aqua Regia Digestion
Li, Lithium (ppm) 4.22 0.75 3.76 4.68 Aqua Regia Digestion
Mg, Magnesium (wt.%) 0.813 0.030 0.785 0.842 Aqua Regia Digestion
Mn, Manganese (wt.%) 0.016 0.001 0.015 0.016 Aqua Regia Digestion
Mo, Molybdenum (ppm) 21.1 0.94 20.3 21.9 Aqua Regia Digestion
Ni, Nickel (ppm) 40.1 2.10 38.3 41.9 Aqua Regia Digestion
P, Phosphorus (wt.%) 0.055 0.003 0.053 0.058 Aqua Regia Digestion
Pb, Lead (ppm) 17.2 0.93 16.4 18.0 Aqua Regia Digestion
Rb, Rubidium (ppm) 14.1 1.23 13.2 14.9 Aqua Regia Digestion
Re, Rhenium (ppm) 0.028 0.002 0.026 0.031 Aqua Regia Digestion
S, Sulphur (wt.%) 2.20 0.085 2.14 2.25 Aqua Regia Digestion
Sb, Antimony (ppm) 125 10 119 131 Aqua Regia Digestion
Sc, Scandium (ppm) 2.63 0.194 2.50 2.75 Aqua Regia Digestion
Se, Selenium (ppm) 2.44 0.30 2.06 2.83 Aqua Regia Digestion
Sn, Tin (ppm) 1.47 0.113 1.36 1.58 Aqua Regia Digestion
Sr, Strontium (ppm) 28.8 1.73 27.7 30.0 Aqua Regia Digestion
Ta, Tantalum (ppm) < 0.010 IND IND IND Aqua Regia Digestion
Tb, Terbium (ppm) 0.30 0.015 0.27 0.32 Aqua Regia Digestion
Te, Tellurium (ppm) 1.89 0.152 1.75 2.03 Aqua Regia Digestion
Th, Thorium (ppm) 3.72 0.285 3.50 3.94 Aqua Regia Digestion
Ti, Titanium (wt.%) < 0.005 IND IND IND Aqua Regia Digestion
Tl, Thallium (ppm) 40.9 2.38 38.9 42.8 Aqua Regia Digestion
U, Uranium (ppm) 3.26 0.205 3.11 3.42 Aqua Regia Digestion
V, Vanadium (ppm) 83 9 78 88 Aqua Regia Digestion
W, Tungsten (ppm) 30.3 2.74 28.2 32.4 Aqua Regia Digestion
Y, Yttrium (ppm) 8.45 0.475 8.08 8.82 Aqua Regia Digestion
Yb, Ytterbium (ppm) 0.50 0.018 0.48 0.53 Aqua Regia Digestion
Zn, Zinc (ppm) 167 6 162 172 Aqua Regia Digestion
Zr, Zirconium (ppm) 5.72 0.71 5.30 6.13 Aqua Regia Digestion
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