First, using drilling survey data, the geometric contours of the deposit are defined, followed by calculations of volume, concentration (metal grade), and finally the tonnage of metal.
The geologist, based on drilling data and knowledge of the geological context, establishes an initial geological model aimed at correlating the different geological bodies with each other, including the mineralized bodies.
It is necessary to establish a cutoff grade (minimum metal content) to geographically and quantitatively define the limits of the mineralized bodies.
Consideration must also be given to exploitation constraints, such as the minimum exploitable width.
The geological model, initially in the form of interpreted sections, evolves into a numerical model using computer modelling tools.
The numerical model provides a spatial representation of the mineralized bodies. It is from this model that the mineralized envelope is defined.
The mineralized envelope is then virtually divided into blocks. The block size is chosen based on the drilling grid and exploitation constraints.
Each block is then assigned a metal grade based on the fragmented knowledge of grades provided by the drill holes.
This assignment is carried out using geostatistical methods that consider the spatial variability of the grade and the difference in volume between measurements and blocks. The result of this step allows for the calculation of resources.
In calculating resources, there are no economic considerations or precise information about potential mining operations.
At this stage, the cutoff grade is semi-quantitative, and resources are generally calculated for a range of cutoff grades. It is not yet possible to answer the question, “How much metal can I recover?
In conclusion, the process of calculating mineral resources from drilling survey data is a critical step in the evaluation of a deposit’s potential. By establishing a comprehensive geological model and utilizing geostatistical methods to assign metal grades to spatially defined blocks, we can accurately quantify the extent and quality of mineralized bodies.
Although this assessment does not account for economic factors or recoverable metal, it provides a foundational understanding of the resource’s viability. This systematic approach not only aids in informed decision-making for future exploration and development but also sets the stage for more detailed economic evaluations that will ultimately determine the feasibility of mining operations.
