Preparation of Mercury Standards from Taconite

Abstract

To provide taconite-based standards for mercury analysis, samples of Sag Mill Discharge, Final Concentrate and Fired Pellets were taken at NSPC. The samples were stage crushed and pulverized to minus 200 mesh at Coleraine. They were well blended, and three portions of each sample were sent to 10 certified laboratories. Duplicate mercury analyses were run on each of the three portions~ therefore, each lab provided six analyses of each sample. In addition, three certified rock or soil samples were sent to each laboratory for analysis. The criterion for the laboratories was a detection limit of not greater than 0.010 mg/kg (10 ppb). Three of the laboratories reported detection limits greater that 10 ppb and the results from these laboratories were not used. The fired pellet mercury content was so low that only two laboratories reported any values, and those were in the range of 1 ppb. Paired t-Tests on the results for the concentrate and Sag Mill Discharge samples indicated that the results from five laboratories could be used for the concentrate sample and from six laboratories for the Sag Mill Discharge sample. Using the above results, the concentrate contained 0.014 mg/kg (14 ppb) mercury with confidence limits (95%) of+/- 0.0012 mg/kg (1.2 ppb), and the Sag Mill Discharge contained 0.020 kg/mg (20 ppb) mercury with confidence limits (95%) of0.0014 mg/kg (1.4 ppb).