OREAS 264b

OREAS 264b was prepared from a blend of dolomite, black slate and a small addition of oxide ore. The ore was sourced from the Carlin Trend in Eureka County, northeastern Nevada. The material was provided by Nevada Gold Mines, operated under Barrick’s management. The deposit is hosted in carbonate rocks, where gold occurs as fine-grained, disseminated Carlin-type mineralisation associated with pyrite and arsenian pyrite in decalcified and weakly silicified zones. OREAS 264b is sourced from the oxide zone and is low in sulphur but remains partly refractory due to carbonaceous (organic) matter. Gold occurs as submicroscopic inclusions within residual sulphides and is also adsorbed onto organic carbon surfaces, which can exhibit 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 520 -550 g
  • Total C 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) 0.358 0.015 0.354 0.363 Pb Fire Assay
Au, Gold (ppm) 0.371 0.010 Bi Fire Assay
Au, Gold (ppm) 0.355 0.023 0.350 0.359 PhotonAssay
C, Carbon (wt.%) 7.10 0.170 6.97 7.23 Infrared Combustion
Ag, Silver (ppm) 0.203 0.017 0.180 0.227 4-Acid Digestion
Al, Aluminium (wt.%) 3.00 0.117 2.91 3.09 4-Acid Digestion
As, Arsenic (ppm) 48.0 2.24 45.5 50.5 4-Acid Digestion
Ba, Barium (ppm) 835 29 815 856 4-Acid Digestion
Be, Beryllium (ppm) 1.06 0.092 0.97 1.14 4-Acid Digestion
Bi, Bismuth (ppm) 0.20 0.010 0.18 0.22 4-Acid Digestion
Ca, Calcium (wt.%) 10.60 0.299 10.23 10.97 4-Acid Digestion
Cd, Cadmium (ppm) 0.18 0.02 0.15 0.20 4-Acid Digestion
Ce, Cerium (ppm) 36.3 1.87 34.8 37.8 4-Acid Digestion
Co, Cobalt (ppm) 0.84 0.13 0.74 0.94 4-Acid Digestion
Cr, Chromium (ppm) 39.6 6.0 36.0 43.2 4-Acid Digestion
Cs, Caesium (ppm) 1.96 0.075 1.87 2.05 4-Acid Digestion
Cu, Copper (ppm) 21.5 1.14 20.2 22.8 4-Acid Digestion
Dy, Dysprosium (ppm) 1.63 0.131 1.50 1.76 4-Acid Digestion
Er, Erbium (ppm) 0.84 0.049 0.78 0.90 4-Acid Digestion
Eu, Europium (ppm) 0.57 0.09 0.49 0.66 4-Acid Digestion
Fe, Iron (wt.%) 1.32 0.046 1.28 1.35 4-Acid Digestion
Ga, Gallium (ppm) 8.27 0.367 7.82 8.73 4-Acid Digestion
Gd, Gadolinium (ppm) 2.31 0.102 2.18 2.44 4-Acid Digestion
Hf, Hafnium (ppm) 1.47 0.121 1.33 1.61 4-Acid Digestion
Ho, Holmium (ppm) 0.29 0.022 0.26 0.32 4-Acid Digestion
In, Indium (ppm) 0.030 0.003 0.024 0.035 4-Acid Digestion
K, Potassium (wt.%) 1.38 0.088 1.33 1.43 4-Acid Digestion
La, Lanthanum (ppm) 20.4 0.84 19.6 21.1 4-Acid Digestion
Li, Lithium (ppm) 12.6 1.4 11.8 13.4 4-Acid Digestion
Lu, Lutetium (ppm) 0.13 0.010 0.11 0.15 4-Acid Digestion
Mg, Magnesium (wt.%) 5.95 0.162 5.80 6.09 4-Acid Digestion
Mn, Manganese (wt.%) 0.059 0.002 0.058 0.061 4-Acid Digestion
Mo, Molybdenum (ppm) 3.97 0.206 3.74 4.19 4-Acid Digestion
Na, Sodium (wt.%) 0.062 0.010 0.057 0.066 4-Acid Digestion
Nb, Niobium (ppm) 3.17 0.85 2.72 3.63 4-Acid Digestion
Nd, Neodymium (ppm) 16.7 0.99 15.6 17.7 4-Acid Digestion
Ni, Nickel (ppm) 5.41 0.77 4.93 5.89 4-Acid Digestion
P, Phosphorus (wt.%) 0.017 0.001 0.016 0.018 4-Acid Digestion
Pb, Lead (ppm) 12.4 0.48 11.8 13.1 4-Acid Digestion
Pr, Praseodymium (ppm) 4.57 0.253 4.28 4.87 4-Acid Digestion
Rb, Rubidium (ppm) 77 4.6 74 80 4-Acid Digestion
S, Sulphur (ppm) 399 17 381 416 4-Acid Digestion
Sb, Antimony (ppm) 4.22 0.260 4.03 4.41 4-Acid Digestion
Sc, Scandium (ppm) 5.50 0.357 5.15 5.85 4-Acid Digestion
Sm, Samarium (ppm) 3.07 0.160 2.78 3.36 4-Acid Digestion
Sn, Tin (ppm) 1.68 0.130 1.58 1.79 4-Acid Digestion
Sr, Strontium (ppm) 45.0 2.03 43.7 46.4 4-Acid Digestion
Tb, Terbium (ppm) 0.32 0.023 0.29 0.35 4-Acid Digestion
Te, Tellurium (ppm) < 0.050 IND IND IND 4-Acid Digestion
Th, Thorium (ppm) 6.99 0.413 6.57 7.42 4-Acid Digestion
Ti, Titanium (wt.%) 0.116 0.013 0.110 0.123 4-Acid Digestion
Tl, Thallium (ppm) 0.69 0.041 0.64 0.73 4-Acid Digestion
Tm, Thulium (ppm) 0.12 0.011 0.10 0.14 4-Acid Digestion
U, Uranium (ppm) 2.83 0.124 2.69 2.98 4-Acid Digestion
V, Vanadium (ppm) 117 6 112 121 4-Acid Digestion
W, Tungsten (ppm) 1.58 0.16 1.44 1.72 4-Acid Digestion
Y, Yttrium (ppm) 8.25 0.722 7.69 8.81 4-Acid Digestion
Yb, Ytterbium (ppm) 0.82 0.054 0.74 0.90 4-Acid Digestion
Zn, Zinc (ppm) 28.5 2.42 26.9 30.1 4-Acid Digestion
Zr, Zirconium (ppm) 49.1 5.0 45.8 52.3 4-Acid Digestion
Ag, Silver (ppm) 0.102 0.014 0.087 0.116 Aqua Regia Digestion
Al, Aluminium (wt.%) 0.240 0.031 0.220 0.259 Aqua Regia Digestion
As, Arsenic (ppm) 47.0 2.00 44.3 49.6 Aqua Regia Digestion
Au, Gold (ppm) 0.149 0.018 0.129 0.169 Aqua Regia Digestion
B, Boron (ppm) < 10.0 IND IND IND Aqua Regia Digestion
Ba, Barium (ppm) 59 9 52 66 Aqua Regia Digestion
Be, Beryllium (ppm) 0.22 0.04 0.19 0.26 Aqua Regia Digestion
Bi, Bismuth (ppm) 0.13 0.02 0.12 0.15 Aqua Regia Digestion
Ca, Calcium (wt.%) 10.62 0.637 10.23 11.02 Aqua Regia Digestion
Cd, Cadmium (ppm) 0.17 0.013 0.15 0.19 Aqua Regia Digestion
Ce, Cerium (ppm) 27.4 1.88 25.8 28.9 Aqua Regia Digestion
Co, Cobalt (ppm) 0.73 0.14 0.63 0.82 Aqua Regia Digestion
Cr, Chromium (ppm) 12.1 1.06 11.2 13.0 Aqua Regia Digestion
Cs, Caesium (ppm) 0.47 0.05 0.43 0.52 Aqua Regia Digestion
Cu, Copper (ppm) 21.2 1.37 20.1 22.4 Aqua Regia Digestion
Fe, Iron (wt.%) 1.20 0.039 1.17 1.24 Aqua Regia Digestion
Ga, Gallium (ppm) 0.67 0.09 0.57 0.77 Aqua Regia Digestion
Hf, Hafnium (ppm) 0.20 0.03 0.17 0.23 Aqua Regia Digestion
Hg, Mercury (ppm) 0.15 0.02 0.12 0.17 Aqua Regia Digestion
In, Indium (ppm) 0.010 0.001 0.009 0.012 Aqua Regia Digestion
K, Potassium (wt.%) 0.167 0.022 0.154 0.180 Aqua Regia Digestion
La, Lanthanum (ppm) 14.3 1.31 13.3 15.2 Aqua Regia Digestion
Li, Lithium (ppm) 1.20 0.26 1.00 1.41 Aqua Regia Digestion
Mg, Magnesium (wt.%) 5.72 0.265 5.50 5.93 Aqua Regia Digestion
Mn, Manganese (wt.%) 0.058 0.003 0.056 0.060 Aqua Regia Digestion
Mo, Molybdenum (ppm) 3.85 0.320 3.62 4.08 Aqua Regia Digestion
Na, Sodium (wt.%) 0.029 0.004 0.027 0.031 Aqua Regia Digestion
Nb, Niobium (ppm) 0.064 0.012 0.052 0.076 Aqua Regia Digestion
Ni, Nickel (ppm) 4.16 0.60 3.75 4.58 Aqua Regia Digestion
P, Phosphorus (wt.%) 0.016 0.001 0.015 0.017 Aqua Regia Digestion
Pb, Lead (ppm) 8.32 1.00 7.61 9.04 Aqua Regia Digestion
Rb, Rubidium (ppm) 8.33 1.03 7.63 9.04 Aqua Regia Digestion
S, Sulphur (ppm) 394 15 381 408 Aqua Regia Digestion
Sb, Antimony (ppm) 3.00 0.39 2.76 3.23 Aqua Regia Digestion
Sc, Scandium (ppm) 1.29 0.24 1.15 1.43 Aqua Regia Digestion
Se, Selenium (ppm) 1.34 0.26 1.13 1.55 Aqua Regia Digestion
Sr, Strontium (ppm) 31.6 2.03 30.1 33.0 Aqua Regia Digestion
Ta, Tantalum (ppm) < 0.010 IND IND IND Aqua Regia Digestion
Tb, Terbium (ppm) 0.22 0.021 0.19 0.26 Aqua Regia Digestion
Th, Thorium (ppm) 4.52 0.50 4.15 4.89 Aqua Regia Digestion
Ti, Titanium (wt.%) < 0.005 IND IND IND Aqua Regia Digestion
Tl, Thallium (ppm) 0.18 0.017 0.17 0.20 Aqua Regia Digestion
U, Uranium (ppm) 1.58 0.135 1.48 1.69 Aqua Regia Digestion
V, Vanadium (ppm) 19.9 2.2 18.6 21.1 Aqua Regia Digestion
W, Tungsten (ppm) 0.31 0.04 0.27 0.36 Aqua Regia Digestion
Y, Yttrium (ppm) 3.75 0.273 3.56 3.94 Aqua Regia Digestion
Yb, Ytterbium (ppm) 0.31 0.015 0.28 0.33 Aqua Regia Digestion
Zn, Zinc (ppm) 24.1 1.73 22.8 25.4 Aqua Regia Digestion
Zr, Zirconium (ppm) 5.76 0.74 5.19 6.34 Aqua Regia Digestion
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