We all know that mining for minerals is a global business and its one of the core activities that affects our global economy on a grand scale. When we hear about mining visions of gold mines come to mind with people digging deep underground. Open pit mining on the other hand is relatively unknown. So what is open pit mining and what does it involve?
Open-pit mining, open-cut mining and opencast mining are much the same in design and structure. It is process of mining the surface to extract or minerals from from the bedrock they blast and remove from an open pit or borrow.
A quarry is technically also an open-pit mine but they are generally much smaller and extract more common minerals for building materials and building stone.
Open-pit mines are normally massive. They are mined until the mineral rich belt is exhausted or the over burden becomes too large for it to be profitable. Once the mine has been closed for mining there is a decision to either turn the pit into a landfill or the pit is rehabilitated. In some situations the pit is converted into a lake unless it is not good for the surrounding ecology.
I found an interesting and very well written website – Tacmin Madini – that are open-pit mining optimization company. They maximize mining production along with management systems. They offer a unique customer loyalty program which I have not found elsewhere. The loyalty program includes chartered flights taking their clients to and from the mines in very remote places.
The mine is excavated in such a way to create a road that spirals all the way to the lowest sections and are referred to as benches and are normally stepped at four to six meters depending on the size of machinery and tip-trucks used onsite. To prevent potential rock falls the benches vertical sides, called a batter, are cut the an angle to minimize risks. Variables taken into consideration is how weathered the rock is, the type of rock and how flawed the rock structure is. Depending on the geological structure of the rock, sometimes they need to secure the rock using rock bolts, cable bolts and shotcrete for safety of workers and machinery working in the pit.
Situated on the side of the open-pit mine is usually a haul road that forms a ramp from which tip-trucks can exit the pit to their offload areas. Once the minerals have been processed the excess rock is then deposited nearby and its also structured with benches to maintain stability.
The processed Ore is known as tailings and is looks like a muddy mix of mineral rich deposit as well as a host of other non ferrous minerals. It is transported through large pipes to a settling pond. The excess water is left to evaporate leaving behind the deposit. The dams can be hazardous because of due to sulfide minerals and cyanide which is used to treat gold.