Definition of Open Pit Mining

In countries such as Mexico, Argentina, Bolivia, Chile or Australia open pit mining is practiced, so named because the deposits are on the surface of the earth and not in its inside. Therefore, the concept of open pit mining must be understood in opposition to underground mining.

The open pit mining activity consists of extracting minerals that are very useful to obtain all kinds of raw materials, especially gold, silver, rhodium and platinum. These minerals are used in the elaboration of electronic devices or for the gold reserves of the institutions banking.

How are minerals obtained?

To extract the minerals, the first step consists of the fragmentation of the rocks by means of a blasting system. To carry out the blasting process, an explosive with an oxidizing agent (usually ammonium nitrate) is used and then the ground is detoned. This initial phase is carried out with all kinds of safety to minimize the impact on the environment and reduce risks to workers. So that the blasting system does not negatively affect the stability of the land near the mine, seismographs are often used.

In the next phase, the rocks are transported to plants where the crushing or grinding process takes place. Grinding is carried out in several stages:

1) Large rocks are used in primary crushing,

2) then the rocks go to a secondary and tertiary crushing circuit and

3) The resulting end product is less than one inch in size.

When the rocks are already crushed, there are two possible options: if the fragmented rock is an oxide It is transported by specialized trucks and if the rock is a sulfur it is sent to a mill where the mineral turns to sand.

The environmental impact of open pit mining

Although companies in this sector have to comply with strict regulations that respect the environment environment, this mining modality generates an evident negative impact. On the one hand, products such as cyanide, lead or sulfuric acid are used and this affects the quality ground and groundwater. At the same time, the ecosystems near the mines are altered and the flora and fauna stop regenerating according to natural cycles.

To the margin of the polluting effects, this activity has a negative impact on the tourism or in relation to the indigenous populations near these deposits.

Photos: Fotolia - Agnormark / Sergei Dvornikov