OREAS 249

OREAS 249 was prepared from a blend of high-grade gold-antimony ore, barren metasediments and Sb-Au concentrate. The ore and concentrate were sourced from the Costerfield Operation (Mandalay Resources Ltd), located ~10 km northeast of Heathcote, Victoria. The deposit is hosted in Lower Silurian metasedimentary rocks and is characterised by narrow, high-grade quartz-stibnite veins. Gold occurs with arsenopyrite and pyrite, as well as in “gold-only” quartz-carbonate veins at depth or beneath stibnite lodes.

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

  • Gold by fire assay with AAS, ICP-OES or ICP-MS finish
  • Gold by PhotonAssay™ with a recommended gross fill mass of 350-380 g
  • Gold by 15-50g aqua regia digestion with ICP-MS and AAS finish
  • Antimony by peroxide fusion with ICP-OES and/or ICP-MS finish
  • Antimony by borate fusion with XRF finish
  • 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) 22.15 0.814 21.84 22.46 Pb Fire Assay
Au, Gold (ppm) 23.33 0.489 23.11 23.55 PhotonAssay
Au, Gold (ppm) 20.27 0.680 19.92 20.63 Aqua Regia Digestion (sample weights 10-50g)
Sb, Antimony (wt.%) 8.15 0.414 7.78 8.52 Peroxide Fusion ICP
Sb, Antimony (wt.%) 8.38 0.149 8.22 8.54 Borate Fusion XRF
Ag, Silver (ppm) 2.22 0.117 2.08 2.36 4-Acid Digestion
Al, Aluminium (wt.%) 5.84 0.203 5.63 6.05 4-Acid Digestion
As, Arsenic (wt.%) 0.182 0.010 0.173 0.191 4-Acid Digestion
Ba, Barium (ppm) 446 46 411 481 4-Acid Digestion
Be, Beryllium (ppm) 2.29 0.062 2.22 2.37 4-Acid Digestion
Bi, Bismuth (ppm) 3.58 0.40 3.32 3.84 4-Acid Digestion
Ca, Calcium (wt.%) 0.579 0.019 0.560 0.597 4-Acid Digestion
Cd, Cadmium (ppm) 0.31 0.04 0.27 0.35 4-Acid Digestion
Ce, Cerium (ppm) 69 4.5 65 73 4-Acid Digestion
Co, Cobalt (ppm) 21.6 2.6 19.5 23.6 4-Acid Digestion
Cr, Chromium (ppm) 196 7 188 203 4-Acid Digestion
Cs, Caesium (ppm) 11.7 0.43 11.1 12.2 4-Acid Digestion
Cu, Copper (ppm) 257 15 245 268 4-Acid Digestion
Er, Erbium (ppm) 1.59 0.26 1.21 1.97 4-Acid Digestion
Fe, Iron (wt.%) 3.90 0.114 3.77 4.03 4-Acid Digestion
Ga, Gallium (ppm) 15.0 1.37 13.9 16.0 4-Acid Digestion
Gd, Gadolinium (ppm) 3.83 0.38 3.20 4.45 4-Acid Digestion
Hf, Hafnium (ppm) 2.86 0.143 2.70 3.02 4-Acid Digestion
Ho, Holmium (ppm) 0.55 0.08 0.44 0.66 4-Acid Digestion
In, Indium (ppm) 0.097 0.016 0.071 0.124 4-Acid Digestion
K, Potassium (wt.%) 2.52 0.069 2.45 2.59 4-Acid Digestion
La, Lanthanum (ppm) 37.9 3.05 35.7 40.1 4-Acid Digestion
Li, Lithium (ppm) 25.0 7.4 19.9 30.1 4-Acid Digestion
Lu, Lutetium (ppm) 0.27 0.03 0.22 0.32 4-Acid Digestion
Mg, Magnesium (wt.%) 1.16 0.036 1.12 1.19 4-Acid Digestion
Mn, Manganese (wt.%) 0.072 0.004 0.069 0.075 4-Acid Digestion
Mo, Molybdenum (ppm) 15.1 3.2 13.0 17.2 4-Acid Digestion
Na, Sodium (wt.%) 0.330 0.009 0.319 0.341 4-Acid Digestion
Nb, Niobium (ppm) 9.42 1.66 8.10 10.75 4-Acid Digestion
Nd, Neodymium (ppm) 30.3 1.21 28.2 32.4 4-Acid Digestion
Ni, Nickel (ppm) 65 8 59 71 4-Acid Digestion
P, Phosphorus (wt.%) 0.048 0.002 0.045 0.050 4-Acid Digestion
Pb, Lead (ppm) 271 28 252 290 4-Acid Digestion
Pr, Praseodymium (ppm) 7.96 0.735 6.92 9.01 4-Acid Digestion
Rb, Rubidium (ppm) 154 7 147 160 4-Acid Digestion
Re, Rhenium (ppm) 0.032 0.004 0.027 0.036 4-Acid Digestion
S, Sulphur (wt.%) 4.25 0.071 4.15 4.36 4-Acid Digestion
Sb, Antimony (wt.%) 7.03 1.54 5.27 8.79 4-Acid Digestion
Sc, Scandium (ppm) 11.1 0.35 10.4 11.8 4-Acid Digestion
Se, Selenium (ppm) 13.8 1.4 12.4 15.3 4-Acid Digestion
Sm, Samarium (ppm) 5.48 0.378 4.90 6.07 4-Acid Digestion
Sr, Strontium (ppm) 130 3 125 135 4-Acid Digestion
Tb, Terbium (ppm) 0.53 0.10 0.41 0.65 4-Acid Digestion
Th, Thorium (ppm) 13.9 0.97 13.1 14.7 4-Acid Digestion
Ti, Titanium (wt.%) 0.249 0.057 0.213 0.285 4-Acid Digestion
Tl, Thallium (ppm) 0.95 0.12 0.87 1.04 4-Acid Digestion
U, Uranium (ppm) 2.43 0.164 2.30 2.56 4-Acid Digestion
V, Vanadium (ppm) 67 5.6 63 72 4-Acid Digestion
W, Tungsten (ppm) 5.06 1.21 3.90 6.23 4-Acid Digestion
Y, Yttrium (ppm) 15.8 2.4 14.2 17.4 4-Acid Digestion
Yb, Ytterbium (ppm) 1.66 0.160 1.42 1.91 4-Acid Digestion
Zn, Zinc (ppm) 250 27 232 267 4-Acid Digestion
Zr, Zirconium (ppm) 98 4.4 94 103 4-Acid Digestion
Ag, Silver (ppm) 2.17 0.049 2.09 2.25 Aqua Regia Digestion
Al, Aluminium (wt.%) 1.03 0.082 0.95 1.11 Aqua Regia Digestion
Ba, Barium (ppm) 94 25 77 112 Aqua Regia Digestion
Be, Beryllium (ppm) 0.92 0.082 0.85 0.99 Aqua Regia Digestion
Bi, Bismuth (ppm) 3.73 0.315 3.44 4.01 Aqua Regia Digestion
Ca, Calcium (wt.%) 0.550 0.021 0.532 0.568 Aqua Regia Digestion
Cd, Cadmium (ppm) 0.31 0.024 0.28 0.34 Aqua Regia Digestion
Ce, Cerium (ppm) 26.4 3.7 23.3 29.5 Aqua Regia Digestion
Co, Cobalt (ppm) 24.2 1.11 23.0 25.5 Aqua Regia Digestion
Cr, Chromium (ppm) 86 7.7 80 91 Aqua Regia Digestion
Cs, Caesium (ppm) 4.13 0.50 3.74 4.52 Aqua Regia Digestion
Cu, Copper (ppm) 266 7 259 273 Aqua Regia Digestion
Fe, Iron (wt.%) 3.55 0.103 3.46 3.64 Aqua Regia Digestion
Ga, Gallium (ppm) 3.21 0.320 2.92 3.51 Aqua Regia Digestion
Hf, Hafnium (ppm) < 0.020 IND IND IND Aqua Regia Digestion
Hg, Mercury (ppm) 0.35 0.026 0.31 0.40 Aqua Regia Digestion
In, Indium (ppm) 0.074 0.005 0.065 0.084 Aqua Regia Digestion
K, Potassium (wt.%) 0.480 0.023 0.459 0.502 Aqua Regia Digestion
La, Lanthanum (ppm) 15.4 1.50 13.8 16.9 Aqua Regia Digestion
Li, Lithium (ppm) 11.8 1.2 10.9 12.7 Aqua Regia Digestion
Mg, Magnesium (wt.%) 0.870 0.013 0.851 0.889 Aqua Regia Digestion
Mn, Manganese (wt.%) 0.073 0.003 0.070 0.076 Aqua Regia Digestion
Mo, Molybdenum (ppm) 13.5 3.1 11.3 15.6 Aqua Regia Digestion
Na, Sodium (wt.%) 0.033 0.004 0.029 0.036 Aqua Regia Digestion
Nb, Niobium (ppm) 0.047 0.031 0.023 0.070 Aqua Regia Digestion
Ni, Nickel (ppm) 71 2.6 68 75 Aqua Regia Digestion
P, Phosphorus (wt.%) 0.034 0.007 0.029 0.039 Aqua Regia Digestion
Rb, Rubidium (ppm) 28.1 1.97 26.3 30.0 Aqua Regia Digestion
Re, Rhenium (ppm) 0.034 0.002 0.031 0.036 Aqua Regia Digestion
S, Sulphur (wt.%) 4.22 0.108 4.12 4.32 Aqua Regia Digestion
Sb, Antimony (wt.%) 7.63 0.469 6.92 8.35 Aqua Regia Digestion
Sn, Tin (ppm) 5.11 0.181 4.88 5.33 Aqua Regia Digestion
Sr, Strontium (ppm) 88 5.8 84 92 Aqua Regia Digestion
Ta, Tantalum (ppm) < 0.010 IND IND IND Aqua Regia Digestion
Ti, Titanium (wt.%) < 0.005 IND IND IND Aqua Regia Digestion
Tl, Thallium (ppm) 0.45 0.032 0.42 0.48 Aqua Regia Digestion
U, Uranium (ppm) 0.75 0.21 0.59 0.90 Aqua Regia Digestion
V, Vanadium (ppm) 16.1 1.38 14.8 17.4 Aqua Regia Digestion
Y, Yttrium (ppm) 6.06 0.451 5.64 6.48 Aqua Regia Digestion
Zn, Zinc (ppm) 266 7 258 274 Aqua Regia Digestion
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