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).
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 aqua regia digestion (15-50g sample weight) with ICP-MS, AAS or ICP-OES finish (22 laboratories);
- Gold by cyanide leach (20-200g) via a variety of cyanide leach methods (LeachWELL tablets, alkaline added sodium cyanide solution and sodium cyanide liquor with LeachWELL powder) with ICP or AAS finish (20 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).
| CRM Code |
Principle Certified Values |
State |
Matrix |
Mineralization |
| OREAS 273 |
Au 10.76 g/t |
Ag 0.646 ppm |
oxide |
carbonate |
Carlin style |