OREAS 291b

OREAS 291b was prepared from a blend of high-grade gold-antimony ore and barren metasediments. The ore was 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.

Thirty-nine 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 400-430 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) 4.26 0.162 4.20 4.32 Pb Fire Assay
Au, Gold (ppm) 4.42 0.120 4.37 4.47 PhotonAssay
Au, Gold (ppm) 3.95 0.213 3.86 4.05 Aqua Regia Digestion (sample weights 10-50g)
Sb, Antimony (wt.%) 1.56 0.063 1.49 1.63 Peroxide Fusion ICP
Sb, Antimony (wt.%) 1.59 0.025 1.55 1.62 Borate Fusion XRF
Ag, Silver (ppm) 0.325 0.022 0.294 0.357 4-Acid Digestion
Al, Aluminium (wt.%) 7.39 0.225 7.16 7.63 4-Acid Digestion
As, Arsenic (ppm) 401 10 392 409 4-Acid Digestion
Ba, Barium (ppm) 697 31 673 720 4-Acid Digestion
Be, Beryllium (ppm) 2.50 0.088 2.41 2.58 4-Acid Digestion
Bi, Bismuth (ppm) 0.75 0.073 0.69 0.81 4-Acid Digestion
Ca, Calcium (wt.%) 0.383 0.006 0.371 0.395 4-Acid Digestion
Ce, Cerium (ppm) 81 5.0 76 86 4-Acid Digestion
Co, Cobalt (ppm) 15.9 0.64 15.2 16.7 4-Acid Digestion
Cr, Chromium (ppm) 134 3 129 139 4-Acid Digestion
Cs, Caesium (ppm) 11.3 0.33 10.8 11.8 4-Acid Digestion
Cu, Copper (ppm) 53 1.9 51 55 4-Acid Digestion
Dy, Dysprosium (ppm) 3.21 0.233 2.81 3.61 4-Acid Digestion
Er, Erbium (ppm) 1.61 0.17 1.36 1.86 4-Acid Digestion
Eu, Europium (ppm) 1.18 0.044 1.08 1.28 4-Acid Digestion
Fe, Iron (wt.%) 3.85 0.099 3.75 3.95 4-Acid Digestion
Ga, Gallium (ppm) 20.0 0.95 19.1 20.9 4-Acid Digestion
Gd, Gadolinium (ppm) 4.56 0.253 4.11 5.01 4-Acid Digestion
Hf, Hafnium (ppm) 3.79 0.218 3.57 4.00 4-Acid Digestion
Ho, Holmium (ppm) 0.59 0.052 0.51 0.66 4-Acid Digestion
In, Indium (ppm) 0.076 0.010 0.060 0.093 4-Acid Digestion
K, Potassium (wt.%) 3.00 0.088 2.91 3.08 4-Acid Digestion
La, Lanthanum (ppm) 42.0 1.65 39.8 44.1 4-Acid Digestion
Li, Lithium (ppm) 49.3 2.51 47.2 51.4 4-Acid Digestion
Lu, Lutetium (ppm) 0.27 0.03 0.24 0.31 4-Acid Digestion
Mg, Magnesium (wt.%) 1.47 0.049 1.43 1.52 4-Acid Digestion
Mn, Manganese (wt.%) 0.046 0.001 0.045 0.047 4-Acid Digestion
Mo, Molybdenum (ppm) 2.17 0.176 2.00 2.34 4-Acid Digestion
Na, Sodium (wt.%) 0.508 0.014 0.492 0.524 4-Acid Digestion
Nb, Niobium (ppm) 13.0 1.8 11.7 14.2 4-Acid Digestion
Nd, Neodymium (ppm) 35.8 1.10 33.7 38.0 4-Acid Digestion
Ni, Nickel (ppm) 58 2.2 55 60 4-Acid Digestion
P, Phosphorus (wt.%) 0.054 0.002 0.052 0.056 4-Acid Digestion
Pb, Lead (ppm) 48.6 3.24 46.2 51.0 4-Acid Digestion
Pr, Praseodymium (ppm) 9.41 0.619 8.44 10.39 4-Acid Digestion
Rb, Rubidium (ppm) 176 8 169 183 4-Acid Digestion
Re, Rhenium (ppm) 0.004 0.001 0.002 0.005 4-Acid Digestion
S, Sulphur (wt.%) 0.818 0.016 0.798 0.838 4-Acid Digestion
Sb, Antimony (wt.%) 1.41 0.057 1.32 1.50 4-Acid Digestion
Sc, Scandium (ppm) 14.1 0.89 13.3 14.8 4-Acid Digestion
Se, Selenium (ppm) 3.65 0.73 2.98 4.33 4-Acid Digestion
Sm, Samarium (ppm) 6.57 0.252 5.99 7.15 4-Acid Digestion
Sn, Tin (ppm) 4.54 0.87 3.77 5.30 4-Acid Digestion
Sr, Strontium (ppm) 95 2.7 92 98 4-Acid Digestion
Ta, Tantalum (ppm) 1.01 0.077 0.94 1.08 4-Acid Digestion
Tb, Terbium (ppm) 0.60 0.032 0.55 0.66 4-Acid Digestion
Th, Thorium (ppm) 15.9 0.67 15.2 16.6 4-Acid Digestion
Ti, Titanium (wt.%) 0.375 0.040 0.348 0.402 4-Acid Digestion
Tl, Thallium (ppm) 0.93 0.071 0.88 0.98 4-Acid Digestion
U, Uranium (ppm) 2.89 0.161 2.74 3.05 4-Acid Digestion
V, Vanadium (ppm) 100 4 97 104 4-Acid Digestion
Y, Yttrium (ppm) 15.6 0.62 14.9 16.4 4-Acid Digestion
Yb, Ytterbium (ppm) 1.68 0.129 1.46 1.90 4-Acid Digestion
Zn, Zinc (ppm) 120 3 116 123 4-Acid Digestion
Zr, Zirconium (ppm) 129 6 124 134 4-Acid Digestion
Ag, Silver (ppm) 0.310 0.020 0.286 0.334 Aqua Regia Digestion
Al, Aluminium (wt.%) 2.40 0.196 2.26 2.55 Aqua Regia Digestion
As, Arsenic (ppm) 366 23 349 383 Aqua Regia Digestion
Ba, Barium (ppm) 103 4 98 107 Aqua Regia Digestion
Be, Beryllium (ppm) 1.20 0.14 1.10 1.31 Aqua Regia Digestion
Bi, Bismuth (ppm) 0.78 0.041 0.72 0.83 Aqua Regia Digestion
Ca, Calcium (wt.%) 0.250 0.008 0.241 0.258 Aqua Regia Digestion
Cd, Cadmium (ppm) 0.070 0.008 0.053 0.087 Aqua Regia Digestion
Ce, Cerium (ppm) 44.9 4.5 41.1 48.8 Aqua Regia Digestion
Co, Cobalt (ppm) 14.8 0.76 14.1 15.6 Aqua Regia Digestion
Cr, Chromium (ppm) 97 2.8 94 99 Aqua Regia Digestion
Cs, Caesium (ppm) 7.32 0.498 6.93 7.71 Aqua Regia Digestion
Cu, Copper (ppm) 52 1.5 51 54 Aqua Regia Digestion
Fe, Iron (wt.%) 3.44 0.066 3.36 3.52 Aqua Regia Digestion
Ga, Gallium (ppm) 7.40 0.727 6.81 7.99 Aqua Regia Digestion
Ge, Germanium (ppm) 0.097 0.016 0.077 0.117 Aqua Regia Digestion
Hf, Hafnium (ppm) 0.46 0.10 0.38 0.55 Aqua Regia Digestion
Hg, Mercury (ppm) 0.068 0.009 0.056 0.080 Aqua Regia Digestion
In, Indium (ppm) 0.036 0.003 0.032 0.039 Aqua Regia Digestion
K, Potassium (wt.%) 0.863 0.061 0.824 0.903 Aqua Regia Digestion
La, Lanthanum (ppm) 23.1 3.0 20.4 25.8 Aqua Regia Digestion
Li, Lithium (ppm) 35.8 2.96 33.2 38.4 Aqua Regia Digestion
Mg, Magnesium (wt.%) 1.23 0.045 1.20 1.27 Aqua Regia Digestion
Mn, Manganese (wt.%) 0.040 0.001 0.039 0.041 Aqua Regia Digestion
Mo, Molybdenum (ppm) 1.97 0.095 1.86 2.08 Aqua Regia Digestion
Na, Sodium (wt.%) 0.032 0.005 0.028 0.037 Aqua Regia Digestion
Ni, Nickel (ppm) 55 2.3 52 58 Aqua Regia Digestion
P, Phosphorus (wt.%) 0.046 0.002 0.044 0.048 Aqua Regia Digestion
Pb, Lead (ppm) 39.9 2.18 37.8 42.0 Aqua Regia Digestion
Rb, Rubidium (ppm) 77 3.8 72 81 Aqua Regia Digestion
Re, Rhenium (ppm) 0.004 0.001 0.003 0.005 Aqua Regia Digestion
S, Sulphur (wt.%) 0.818 0.016 0.802 0.834 Aqua Regia Digestion
Sb, Antimony (wt.%) 1.26 0.21 1.02 1.51 Aqua Regia Digestion
Sc, Scandium (ppm) 6.29 0.485 5.86 6.72 Aqua Regia Digestion
Se, Selenium (ppm) 2.94 0.171 2.60 3.28 Aqua Regia Digestion
Sn, Tin (ppm) 1.80 0.126 1.67 1.93 Aqua Regia Digestion
Sr, Strontium (ppm) 34.2 2.06 32.5 35.8 Aqua Regia Digestion
Ta, Tantalum (ppm) < 0.010 IND IND IND Aqua Regia Digestion
Te, Tellurium (ppm) 0.057 0.011 0.041 0.073 Aqua Regia Digestion
Th, Thorium (ppm) 11.3 0.96 10.5 12.2 Aqua Regia Digestion
Ti, Titanium (wt.%) 0.095 0.005 0.092 0.099 Aqua Regia Digestion
Tl, Thallium (ppm) 0.54 0.050 0.50 0.57 Aqua Regia Digestion
U, Uranium (ppm) 1.41 0.138 1.31 1.52 Aqua Regia Digestion
V, Vanadium (ppm) 60 1.3 58 62 Aqua Regia Digestion
W, Tungsten (ppm) 0.93 0.19 0.74 1.12 Aqua Regia Digestion
Y, Yttrium (ppm) 8.01 0.752 7.45 8.57 Aqua Regia Digestion
Zn, Zinc (ppm) 109 3 106 112 Aqua Regia Digestion
Zr, Zirconium (ppm) 16.1 2.3 14.0 18.2 Aqua Regia Digestion
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