Sampling of Mineral Deposits

the selection and analysis of samples from various parts of mineral bodies in order to determine their composition and quality. Sampling is essential for evaluating a deposit, calculating its reserves, and selecting the method of extraction and the plan for working the minerals.

There are four types of sampling: chemical, mineralogical, technical, and technological. Chemical sampling is used to determine the amount of useful components and harmful impurities in deposits of metallic and many nonmetallic minerals. Mineralogical sampling establishes the various grades of useful minerals. Technical sampling is used in analyzing minerals whose value depends on such mechanical and physical properties as strength, resistance to compression, wear under friction, flexibility, resistance to fire, resistance to aggressive chemical substances, and electrical conductivity. Technological sampling is used in testing a mineral’s concentration, capacity for melting, or use in unprocessed form.

Regardless of the type of sampling used, the process is divided into three stages: selecting, processing, and analyzing the samples.

Samples are selected in mining excavations by cutting a groove, scratching the surface, taking pieces or lumps, collecting residue from boreholes, or removing part of a rock broken off during the sinking of mining shafts. Samples in mines are selected systematically so that evaluation of the quality of the mineral in the entire deposit or sections of the deposit can be made with the smallest number of samples taken from points that are at definite distance from one another (from 2 to 50 m).

Samples from boreholes opening up deposits of solid minerals are selected by removing specimens from the bottom or walls of the hole using special devices or by flushing out a drilled part of the deposit with a flushing fluid. Samples of petroleum in wells are taken from each petroleum stratum separately. The quality of groundwater is determined on the basis of samples taken in boreholes, wells, and springs.

The most complex type of sample processing is the chemical sampling of solid minerals. The sample, usually weighing several kilograms, is broken down by crushing, mixing, and reduction to chemical samples weighing a few grams. The minimum weight of a chemical sample in the successive stages of processing is monitored according to H. Czeczott’s formula: Q = k ·d², where Q is the weight of the sample in kilograms, d is the diameter of the largest particles of the crushed sample in millimeters, and k is the coefficient of proportionality, which ranges from 0.05 to 0.8.

In chemical sampling existing chemical methods are used to analyze samples to determine the content of valuable elements and harmful impurities. Technical analysis reveals mechanical and other physical properties, and technological analysis determines the most efficient ways of working, processing, and using the minerals. For some types of mineral products, chemical sampling methods have been developed that can be used at the faces of mines and boreholes without taking samples. This method uses the properties of the mineral and the chemical composition of minerals that can be subjected to quantitative evaluation by special instruments at the site of the mineral raw material.