OREAS 273

OREAS 273 was prepared from high-grade oxidised gold ore from the Cortez Mine located in Lander and Eureka County, Nevada, USA. The mine is located on the Carlin Trend approximately 75 miles (120 km) southwest of Elko and is owned by Nevada Gold Mines (operated by Barrick).

Carlin-style gold mineralisation is notorious for its refractory nature. The significant presence of carbonaceous material impedes gold recovery by aqua regia digestion and cyanide leach methods. Matching your standards to the matrix and mineralisation style of your field samples as well as the analytical method used for sample analysis is very important, as a mismatch could result in low gold recovery.

Thirty-one commercial analytical laboratories participated in the program to certify the elements shown below. The following methods were employed:

  • Gold by fire assay (15-40g charge weight) with AAS, ICP-OES or ICP-MS finish (31 laboratories);
  • Gold by x-ray photon assay on ~350g sample weights using 4 Chrysos PhotonAssay machines at 3 laboratories. Multiple rounds of data (comprising three or six replicates) were generated by different staff from 3 of the machines;
  • Full ICP-OES and ICP-MS elemental suites by aqua regia digestion (up to 25 laboratories depending on the element);
  • Full ICP-OES and ICP-MS elemental suites by 4-acid (HNO3-HF-HClO4-HCl) digestion (up to 25 laboratories depending on the element).
Analyte Certified Value 1SD 95% Confidence Low 95% Confidence High Method
Au, Gold (ppm) 10.76 0.334 10.64 10.87 Pb Fire Assay
Au, Gold (ppm) 10.72 0.260 10.21 11.23 X-ray Photon Assay
Ag, Silver (ppm) 0.646 0.027 0.635 0.657 4-Acid Digestion
Al, Aluminium (wt.%) 1.65 0.097 1.61 1.70 4-Acid Digestion
As, Arsenic (ppm) 1211 69 1180 1241 4-Acid Digestion
Ba, Barium (ppm) 44.3 2.22 43.3 45.3 4-Acid Digestion
Be, Beryllium (ppm) 0.54 0.034 0.52 0.55 4-Acid Digestion
Bi, Bismuth (ppm) 0.64 0.033 0.62 0.66 4-Acid Digestion
Ca, Calcium (wt.%) 19.43 1.221 18.88 19.98 4-Acid Digestion
Cd, Cadmium (ppm) 0.42 0.028 0.40 0.43 4-Acid Digestion
Ce, Cerium (ppm) 22.8 1.54 22.2 23.5 4-Acid Digestion
Co, Cobalt (ppm) 2.21 0.139 2.14 2.27 4-Acid Digestion
Cr, Chromium (ppm) 32.9 4.1 31.2 34.6 4-Acid Digestion
Cs, Caesium (ppm) 3.05 0.117 3.00 3.10 4-Acid Digestion
Cu, Copper (ppm) 20.9 1.48 20.3 21.5 4-Acid Digestion
Dy, Dysprosium (ppm) 2.95 0.150 2.86 3.04 4-Acid Digestion
Er, Erbium (ppm) 1.83 0.097 1.77 1.90 4-Acid Digestion
Eu, Europium (ppm) 0.56 0.034 0.54 0.59 4-Acid Digestion
Fe, Iron (wt.%) 0.784 0.030 0.772 0.797 4-Acid Digestion
Ga, Gallium (ppm) 4.45 0.350 4.29 4.62 4-Acid Digestion
Gd, Gadolinium (ppm) 2.88 0.180 2.78 2.99 4-Acid Digestion
Ge, Germanium (ppm) 0.14 0.03 0.12 0.16 4-Acid Digestion
Hf, Hafnium (ppm) 0.90 0.072 0.87 0.92 4-Acid Digestion
Ho, Holmium (ppm) 0.63 0.044 0.59 0.66 4-Acid Digestion
In, Indium (ppm) 0.035 0.005 0.033 0.037 4-Acid Digestion
K, Potassium (wt.%) 0.778 0.043 0.760 0.796 4-Acid Digestion
La, Lanthanum (ppm) 18.7 1.23 18.1 19.3 4-Acid Digestion
Li, Lithium (ppm) 11.8 0.64 11.5 12.0 4-Acid Digestion
Lu, Lutetium (ppm) 0.22 0.017 0.21 0.23 4-Acid Digestion
Mg, Magnesium (wt.%) 5.19 0.215 5.10 5.29 4-Acid Digestion
Mn, Manganese (wt.%) 0.041 0.001 0.041 0.042 4-Acid Digestion
Mo, Molybdenum (ppm) 7.42 0.279 7.31 7.52 4-Acid Digestion
Na, Sodium (wt.%) 0.031 0.006 0.029 0.034 4-Acid Digestion
Nb, Niobium (ppm) 3.82 0.297 3.68 3.95 4-Acid Digestion
Nd, Neodymium (ppm) 13.9 0.59 13.6 14.3 4-Acid Digestion
Ni, Nickel (ppm) 31.2 1.91 30.3 32.0 4-Acid Digestion
P, Phosphorus (wt.%) 0.103 0.005 0.101 0.105 4-Acid Digestion
Pb, Lead (ppm) 12.2 0.75 11.8 12.6 4-Acid Digestion
Pr, Praseodymium (ppm) 3.57 0.164 3.48 3.67 4-Acid Digestion
Rb, Rubidium (ppm) 59 3.1 58 61 4-Acid Digestion
Re, Rhenium (ppm) 0.007 0.001 0.007 0.007 4-Acid Digestion
S, Sulphur (wt.%) 0.049 0.007 0.046 0.052 4-Acid Digestion
Sb, Antimony (ppm) 26.7 1.02 26.3 27.2 4-Acid Digestion
Sc, Scandium (ppm) 4.00 0.252 3.88 4.11 4-Acid Digestion
Se, Selenium (ppm) 9.97 1.08 9.28 10.66 4-Acid Digestion
Sm, Samarium (ppm) 2.65 0.081 2.62 2.69 4-Acid Digestion
Sn, Tin (ppm) 0.97 0.086 0.93 1.00 4-Acid Digestion
Sr, Strontium (ppm) 321 19 313 329 4-Acid Digestion
Ta, Tantalum (ppm) 0.25 0.03 0.23 0.27 4-Acid Digestion
Tb, Terbium (ppm) 0.45 0.033 0.43 0.47 4-Acid Digestion
Te, Tellurium (ppm) 0.21 0.03 0.20 0.22 4-Acid Digestion
Th, Thorium (ppm) 2.94 0.116 2.89 2.99 4-Acid Digestion
Ti, Titanium (wt.%) 0.084 0.004 0.082 0.086 4-Acid Digestion
Tl, Thallium (ppm) 9.47 0.363 9.31 9.64 4-Acid Digestion
Tm, Thulium (ppm) 0.25 0.010 0.24 0.25 4-Acid Digestion
U, Uranium (ppm) 6.22 0.302 6.10 6.35 4-Acid Digestion
V, Vanadium (ppm) 111 6 109 113 4-Acid Digestion
W, Tungsten (ppm) 10.5 0.49 10.3 10.8 4-Acid Digestion
Y, Yttrium (ppm) 24.9 1.19 24.4 25.3 4-Acid Digestion
Yb, Ytterbium (ppm) 1.57 0.086 1.52 1.62 4-Acid Digestion
Zn, Zinc (ppm) 46.4 3.62 44.9 47.9 4-Acid Digestion
Zr, Zirconium (ppm) 31.5 4.7 29.4 33.5 4-Acid Digestion
Ag, Silver (ppm) 0.524 0.043 0.504 0.545 Aqua Regia Digestion
Al, Aluminium (wt.%) 0.549 0.056 0.524 0.575 Aqua Regia Digestion
As, Arsenic (ppm) 1215 61 1188 1243 Aqua Regia Digestion
Ba, Barium (ppm) 25.1 2.38 23.8 26.3 Aqua Regia Digestion
Be, Beryllium (ppm) 0.40 0.023 0.39 0.41 Aqua Regia Digestion
Bi, Bismuth (ppm) 0.61 0.024 0.60 0.62 Aqua Regia Digestion
Ca, Calcium (wt.%) 18.56 1.328 17.88 19.25 Aqua Regia Digestion
Cd, Cadmium (ppm) 0.42 0.027 0.41 0.43 Aqua Regia Digestion
Ce, Cerium (ppm) 16.2 1.15 15.6 16.7 Aqua Regia Digestion
Co, Cobalt (ppm) 2.24 0.30 2.09 2.39 Aqua Regia Digestion
Cr, Chromium (ppm) 22.1 1.94 21.2 23.0 Aqua Regia Digestion
Cs, Caesium (ppm) 1.42 0.20 1.32 1.53 Aqua Regia Digestion
Cu, Copper (ppm) 20.5 1.87 19.7 21.3 Aqua Regia Digestion
Dy, Dysprosium (ppm) 2.89 0.241 2.69 3.08 Aqua Regia Digestion
Er, Erbium (ppm) 1.72 0.117 1.64 1.81 Aqua Regia Digestion
Eu, Europium (ppm) 0.55 0.037 0.50 0.59 Aqua Regia Digestion
Fe, Iron (wt.%) 0.759 0.060 0.732 0.785 Aqua Regia Digestion
Ga, Gallium (ppm) 1.75 0.22 1.63 1.87 Aqua Regia Digestion
Gd, Gadolinium (ppm) 2.83 0.206 2.66 3.00 Aqua Regia Digestion
Ge, Germanium (ppm) < 0.10 IND IND IND Aqua Regia Digestion
Hf, Hafnium (ppm) 0.22 0.03 0.20 0.23 Aqua Regia Digestion
Hg, Mercury (ppm) 96 4.2 94 98 Aqua Regia Digestion
Ho, Holmium (ppm) 0.60 0.052 0.55 0.65 Aqua Regia Digestion
In, Indium (ppm) 0.034 0.004 0.032 0.035 Aqua Regia Digestion
K, Potassium (wt.%) 0.277 0.023 0.267 0.287 Aqua Regia Digestion
La, Lanthanum (ppm) 12.9 0.74 12.5 13.2 Aqua Regia Digestion
Li, Lithium (ppm) 4.37 0.427 4.13 4.61 Aqua Regia Digestion
Lu, Lutetium (ppm) 0.19 0.014 0.18 0.20 Aqua Regia Digestion
Mg, Magnesium (wt.%) 4.87 0.176 4.78 4.96 Aqua Regia Digestion
Mn, Manganese (wt.%) 0.041 0.003 0.039 0.042 Aqua Regia Digestion
Mo, Molybdenum (ppm) 7.36 0.617 7.08 7.63 Aqua Regia Digestion
Nb, Niobium (ppm) 0.11 0.02 0.10 0.12 Aqua Regia Digestion
Nd, Neodymium (ppm) 11.4 0.92 10.6 12.1 Aqua Regia Digestion
Ni, Nickel (ppm) 30.4 2.40 29.3 31.5 Aqua Regia Digestion
P, Phosphorus (wt.%) 0.100 0.011 0.095 0.105 Aqua Regia Digestion
Pb, Lead (ppm) 12.1 1.18 11.5 12.7 Aqua Regia Digestion
Pr, Praseodymium (ppm) 2.74 0.229 2.55 2.93 Aqua Regia Digestion
Rb, Rubidium (ppm) 20.4 2.1 19.3 21.5 Aqua Regia Digestion
Re, Rhenium (ppm) 0.007 0.001 0.006 0.007 Aqua Regia Digestion
S, Sulphur (wt.%) 0.045 0.009 0.040 0.049 Aqua Regia Digestion
Sb, Antimony (ppm) 19.7 2.2 18.7 20.7 Aqua Regia Digestion
Sc, Scandium (ppm) 3.87 0.40 3.68 4.06 Aqua Regia Digestion
Se, Selenium (ppm) 8.97 0.747 8.62 9.32 Aqua Regia Digestion
Sm, Samarium (ppm) 2.39 0.170 2.28 2.50 Aqua Regia Digestion
Sn, Tin (ppm) 0.60 0.08 0.55 0.64 Aqua Regia Digestion
Sr, Strontium (ppm) 308 26 297 320 Aqua Regia Digestion
Ta, Tantalum (ppm) < 0.010 IND IND IND Aqua Regia Digestion
Tb, Terbium (ppm) 0.44 0.033 0.42 0.47 Aqua Regia Digestion
Te, Tellurium (ppm) 0.20 0.04 0.19 0.22 Aqua Regia Digestion
Th, Thorium (ppm) 2.43 0.128 2.37 2.49 Aqua Regia Digestion
Ti, Titanium (wt.%) 0.008 0.002 0.007 0.008 Aqua Regia Digestion
Tl, Thallium (ppm) 7.52 0.77 7.14 7.90 Aqua Regia Digestion
Tm, Thulium (ppm) 0.23 0.008 0.22 0.24 Aqua Regia Digestion
U, Uranium (ppm) 5.07 0.283 4.94 5.20 Aqua Regia Digestion
V, Vanadium (ppm) 60 6 57 63 Aqua Regia Digestion
W, Tungsten (ppm) 5.12 0.456 4.89 5.34 Aqua Regia Digestion
Y, Yttrium (ppm) 23.2 1.32 22.6 23.8 Aqua Regia Digestion
Yb, Ytterbium (ppm) 1.41 0.130 1.32 1.50 Aqua Regia Digestion
Zn, Zinc (ppm) 42.9 3.10 41.6 44.3 Aqua Regia Digestion
Zr, Zirconium (ppm) 7.93 0.652 7.55 8.30 Aqua Regia Digestion
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