To define the ore from the normal rock, samples are taken and tested by the laboratory of the mining construction company. Assay results are used to point out areas of ore and waste rock, which are mined individually. Some harder areas require blasting to slacken the rock before removal by hydraulic diggers. Dump trucks transport the rock to the primary crushers in the open pit from underground.
The primary crushers at the open pit mine site, receive ore and waste at separate times. They divide the larger rocks down to a size suitable for transport on the conveyor belt. Mining Construction Companylike Krishana Mineshave certain regulations to follow this process.
A rubber belted conveyor carries the ore and waste rock from the open pit, roughly a couple of kilometres, through a tunnel by Union Hill, to the mill and waste rock banks. Large electromagnets remove any steel wreckage shovelled from the old Martha Mine workings.
Ore from both open pit and underground is accumulated separately at the mill before being crammed into a S.A.G. mill with lime, water and steel balls. They returned the larger particles from this mill to the S.A.G. mill for more grinding. The finer particles get more grinding in a ball mill and are size divided to give a final product of lesser than 80% microns.
A slurry of ground ore, water and cyanide solution which is not so strong is filled into large steel leach tanks where the gold and silver are dissolved. After this leaching process, the slurry passes through six different adsorption tanks containing carbon granules which adsorb the gold and silver. This process gets rid of 93% of the gold and 70% of the silver. This process explains the mining of gold and silver followed by Mining Construction CompanyKrishna Mines
The loaded carbon is filled into an elution column where the bullion is washed off thoroughly and the barren carbon is recycled. The wash solution which is called a pregnant electrolyte is passed through electrowinning cells where gold and silver are won onto stainless steel cathodes.
The loaded cathodes are washed to yield a gold and silver-bearing residue which is dried, mixed with fluxes and embedded into the furnace. After many hours the molten material is discharged into a cascade of moulds producing bars of Dore bullion.
Some of the leftover water from dewatering the mine, from the embankment under-drains and decant water from the tailings pond, is recycled for use in the crushing circuit. Excess water is drawn to the water treatment plant and treated to the expected standards before discharge into the River.
The mining process generates two by-products:
The dominant rock type that is at the Waihi area is andesite, and it varies from a wholly weathered material to a ‘fresh’ rock. Ignimbrite is also present and its formation also varies completely because of ‘fresh’. There are fewer quantities of sand and ashes that veil the pit area.
A special feature of the normal rock is that some of it contains sulphide and it is proficient in producing acid seepage when flashed to oxygen and water. This rock is transferred to a PAF rock. Normal rock without the probable to form acid drainage is referred to as non-acid forming (NAF) waste rock. Special design and practical procedures are used to manage acid drainage generation. As a possibility, provision is made to obtain and treat any solution that is generated.
Tailings are slurry that has around solids of 30% and are deposited from the crest of the waste rock embankment through a series of spigots. Uncontaminated tailings are delivered above water onto previously placed tailings.
The material is mostly silt size but contains clay and sand grains. Promptly next to the point of deposition into the pond the tailings contain a higher symmetry of sand, because the sand particles tend to settle out more quickly, while on the different side of the pond they contain a higher symmetry of clay. The physical characteristics of the tailings vary parallel across the pond, and this forms tailings ‘beach’ next to the crest.
The sands have low permeability, and as they merge the permeability reduces if they are less permeable than the natural soils that control the embankment. The reducing permeability means that drainage from the tailings mass reduces significantly with time. Consolidation, the permeability of the tailings, decreases by more than a factor of 10 compared with its permeability after initial displacement, to become less than 10-9 metres per second. The permeability of the merged tailings is very low and is similar to that required for the liner of a modern depot.
This is the common process and methodologies used by the one of the best mining Construction Company in the world Krishna Mines to mine mineral from the earth.