Sampling is a statistical technique that means extracting a part (sample) from the whole (population) with the purpose of evaluating certain characteristics of this population.
A good mining project is developed in stages that are previously defined based on results obtained from samples of rock, soil, stream sediment, pan concentrate, water, ROM, plant concentrates, etc., which after their collection have their contents and/or mineralogical composition, specific weight, porosity, humidity, granulometry determined by various techniques of chemical analysis, mineralogical, physical and physicochemical aspects; as well as data samples obtained through structural and geophysical measurements, for example.
Economic evaluation studies, mine planning and performance forecasting of a mining project are based on estimates of ore content and quantity. These estimates, in turn, are based on samples, selected according to a previously defined sampling plan. The more representative the samples, the more precise and accurate the estimates. A sample can be defined as a small fraction of a body or population that summarizes in itself certain characteristics of the whole. For this representativeness to occur, it is necessary to adopt criteria and methods that allow keeping the intrinsic errors of each stage, from sample collection to data interpretation, within acceptable and controlled limits.
What constitutes the sampling process?
The sampling process consists of the removal of modulated quantities of material from a whole that is to be sampled, for the composition of the primary or global sample, in such a way that it is representative of the sampled whole.
Representativeness in a sample occurs when properties such as mineralogical constituents, content of the various elements, particle size distribution, specific mass, etc., estimated based on a sample, present a statistically acceptable variability.
What are the objectives of the sampling process?
The ultimate goal of all sampling is basically to determine a quality parameter, or attribute. The main parameters usually estimated in a sample are:
- Geochemical Contents
- mineralogy
- moisture
- porosity
- density
- magnetic susceptibility.
Sampling in Mineral Prospecting
In the case of a mineral deposit, there is a range of minerals in proportions that vary throughout the body. Consequently, the concentration of the elements also varies from one point to another.
As a result, it is extremely unlikely that a single sample will efficiently and accurately represent the overall composition of the deposit. The sample-related error decreases with increasing number of samples, but it does not disappear. All sampling therefore involves an intrinsic error.
The main objectives of sampling in a mining project involve the representation of mineral deposits themselves and also of the products generated from the processing of the mineralized rocks contained therein, through the determination of their physical and chemical properties.
The results obtained from the physical and chemical analysis of the materials in a given deposit are used to:
(a) interpretation of the processes of deposit formation and its geological modeling;
(b) classification of resources and reserves;
(c) assessment of economic potential;
(e) definition of processes and routes for treatment and industrial transformation;
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