Exploration and Evaluation of Deposits

This chapter is concerned with the process of analyzing an area to find aggregate deposits as well as their resource/reserve evaluation. The information collected during exploration is utilized for assessing the size and quality of the aggregate deposit and for determining if there is the potential for it to be extracted. Two principal stages are outlined in aggregate exploration: reconnaissance exploration and detailed exploration. The main methods applied at different phases are discussed, especially geophysical methods because they are essential in the exploration of a sand and gravel deposit. The methods discussed are organized in order of scale and stage, from photogeology to drilling, through remote sensing and geophysical surveys. Technical and economic/financial methods used for evaluating an aggregate mining project are considered. The technical aspects are related to the geological setting of the deposit and the main characteristics of the material (i.e., tonnage). For this, a general introduction to geostatistics from a conceptual point of view and the principal classical methods utilized in the evaluation process are provided. The economic/financial methods cover the estimation of the principal economic inputs and outputs in the project and the amount, type, and cost of capital forthcoming for a project. Net present value, internal rate of return, payback period values, and risk analysis permits are briefly explained.