OREAS 990b is a copper-gold-silver concentrate certified reference material (CRM) sourced from the Rosebery metallurgical plant owned and operated by MMG Ltd. The Rosebery mine and plant are located in the north-west region of Tasmania, Australia approximately 300 kilometres north-west of Hobart and 125 kilometres south of Burnie. The key minerals of economic importance include sphalerite, galena, pyrite, chalcopyrite and electrum. Fifteen ‘umpire’ laboratories undertook copper, gold, silver and moisture analysis on the sample as received but the results are corrected to a dry sample basis. The term ‘umpire’ here refers to the routine analysis by these laboratories using classical methodologies for precious and base metals. Fifteen geoanalytical laboratories also participated in the program to undertake the following:

• Full elemental suites by peroxide fusion with ICP-OES and MS finish;
• Full elemental suites by 4-acid digestion with ICP-OES and MS finish;
• Total S by IR combustion furnace;
• Gold by instrumental neutron activation analysis (INAA) to confirm homogeneity (undertaken by ANSTO, Lucas Heights).