Industry and business

methods of searching for minerals from the ground

methods of searching for minerals from the ground

The search for minerals is among the initial stages in production processes, and the methods of exploration vary depending on the region and the type of mineral extracted from the Earth’s subsurface. This stage is very challenging and costly, and despite that, it is often an unpredictable process in terms of results.

Mineral exploration is usually conducted in uninhabited or sparsely populated areas, which can be deserts, mountains, forests, or underwater areas. For example, oil production in the Western Desert or the Gulf of Suez in Egypt. Therefore, mineral exploration in such conditions requires significant expenses due to high wages, the need to prepare and provide transportation and service facilities, and accommodation for workers.

The role of geological maps in the exploration process

The search for minerals and their availability locations is crucial to pre-identify their occurrences, types, and the size of reserves that may involve substantial investments. It is necessary to determine the possibility of exploiting these minerals and their importance to industries and the need for them before engaging in the extraction process. Geological maps are essential in the exploration process as they identify the locations of these minerals. Geologists usually choose easily recognizable areas due to weathering factors, especially in river valleys or mountain edges, or through rocks that are visually apparent. Geologists can determine the association of these rocks with specific types of minerals based on their geological history.

In areas where the presence of minerals near the Earth’s surface is not apparent, obtaining sufficient information about the nature of rocks and mineral deposits beneath the surface is necessary. This requires the use of modern exploration methods, which have been developed through advancements in geophysical exploration. Geophysical exploration relies on measuring the natural properties of rocks either on the Earth’s surface or through aerial surveys using specialized aircraft equipped with highly accurate devices to measure properties such as magnetism, electrical conductivity, and radiation. These measurements are then interpreted to determine the type, depth, and composition of rocks, as well as their density, magnetic intensity, electrical conductivity, and elasticity. Different methods are then employed to verify the presence and extract the mineral ores.

Methods of mineral exploration

Engineers and scientists use various methods to search for and extract mineral resources from the Earth’s subsurface. These methods primarily depend on the type of discovered minerals, the properties of the surrounding soil, and the needs of the region. Some of the commonly used methods include:

1- Magnetic Method

This method is used to detect highly magnetic ores, such as magnetite (iron oxide) and pyrite (iron sulfide). It relies on measuring the deviation of a magnetic needle in a magnetometer device from the magnetic meridian in a specific area. The magnetic needle usually aligns with the magnetic meridian when a mineral deposit is present in a particular region, allowing the detection of mineral-bearing areas.

2- Gravity Method

Gravity intensity varies due to the difference in density between adjacent rocks since the Earth’s crust rocks are not homogeneous. The gravity intensity is measured to determine the boundaries between rock masses with different densities using specialized devices such as pendulums or gravimeters. This method has been used to detect heavy ores such as magnetite, nickel, and chromium, as well as light ores like salt and to locate petroleum deposits in subsurface rocks.

3- Electrical Methods

Electrical methods are used to detect copper, iron, lead, and other ores that exhibit electrical conductivity. Two main approaches are utilized: one based on measuring electrical resistance and the other on measuring the voltage difference.

  • Electrical Resistance Measurement Method: This method involves using two electrodes and measuring the voltage drop resulting from the electric current passing through the rock layers between them using a voltmeter. The current flow varies depending on the electrical conductivity of the rocks, and the current intensity is measured using an ammeter. The electrical resistance of each rock layer can be calculated based on these measurements, and the detected ore depth is approximately equal to the electrode spacing. The greater the distance between the electrodes, the deeper the detected ores.
  • Potential Difference Method: This method involves passing an electric current through the rocks of the Earth’s crust using two non-polarized electrodes connected to an amplifier that leads to specialized speakers. One electrode remains fixed in the ground while the other is moved until the speakers receive the lowest sound level. At this point, the electrodes are on the same equipotential line. If the rocks are homogeneous, the equipotential lines will be symmetrically distributed around the electrodes. However, the presence of conductive or resistive bodies buried in the Earth’s crust causes deviations in the equipotential lines.

4- Seismic Method

The speed of sound waves varies in different rocks and minerals due to their elasticity and concentration. The seismic method is used to determine the geological formations present in the Earth’s crust by utilizing the reflection and refraction of sound waves generated by detonating a charge of dynamite on the Earth’s surface. The range and strength of these sound waves vary due to the variation in the nature and density of the medium they pass through. The arrival of sound waves can be recorded using sensitive devices called geophones, which capture the moments of sound wave arrival. The arrival times can also be recorded using instruments called seismometers, allowing the calculation and study of the thickness of the layers traversed by the sound waves by comparing the time between the explosion and the wave’s arrival with geological information about the area to assess the presence of minerals.

5- Radiometric Method

This method is used to measure the radiation emitted by certain mineral elements such as radium, uranium, thorium, and lithium. Due to the variation of minerals in radiation, it can be used to determine their identification and location using complex technical methods. Modern and advanced techniques employ radiation surveys from above the Earth’s surface or through the use of aircraft or satellites.

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