Grade Control in One of the Biggest Open Pit Mines in Europe: Corta Atalaya, Riotinto

Abstract

Grade control refers to the procedure to differentiate ore from waste in a mine. It is usually not easy to make such differentiation, especially in metallic mines where grades are very low, and miners have no visual or texture reference to distinguish the rock. This paper gives details of the grade control process that has been in operation during the last 10 years in the Corta Atalaya open pit, Riotinto, Huelva, Spain. The spacing of the blast boreholes, the sampling procedure, the laboratory analysis, and the software used to interpolate the data are discussed in detail. The amount of data generated is huge, as more than 120,000 boreholes are drilled each year, generating a high workload, as each borehole has to be sampled, each sample analyzed, and the results included in Recmin databases. These data are used to generate separation zones for waste and ore that are marked by topographers. This process is a key part of the mining sequence, directly impacting the economic results of the mine as better leverage of the deposit is obtained.