09 | EDUCENTRE » ABOUT MINING

For centuries mining has been a prime means for creating wealth by supplying the metals and minerals essential to civilized living. There are seven basic steps in the modern mining process that turns mineral ore into base or precious metals. They are:

• Exploration
  
• Engineering
  
• Building a mine
  
• Mining and Processing
  
• Refining
  
• Reclaiming the land

EXPLORaTION

Mineral explorers search for properties that match the geologic profile of the world's most profitable high-grade, low-cost producing mines. Since nature tends to form ore deposits in consistent structures often called geologic "beds", explorers' first focus is to evaluate beds in areas known to be geologically fertile for indicators of metal deposits.

A primary geologic indicator is rock alteration. In the formation of an ore deposit, there is usually a telltale chemical reaction in the layers of rock that could contain a potential mine. This reaction may cause both a mineralogical and/or chemical change – or alteration -- in the rocks. An alteration zone usually covers a much area that the ore deposit itself and leads the explorer to the deposit.

A key geophysical indicator is strong magnetic and/or electromagnetic signatures associated with specific base and precious mineral deposits. Geophysical instruments measure the physical characteristics rocks, both from the air or on the ground in a systematic grid pattern. The goal is to detect anomalies that could indicate a potential ore deposit. Advances in technology allow Magnus International Resources to create 2-D and 3-D geophysical maps to pinpoint the most promising ore bodies.

Another clue to detecting a potential deposit is geochemical anomalies, or areas with a high concentration of metal. Geochemistry provides a method for systematically exploring properties through the measurement of quantities of metal held in rock and/or soil. Since ore deposits that were formed hundreds of millions of years ago have undergone significant weathering, geochemical analysis of the metal content of surface soils can indicate the presence of an ore body. These geochemical anomalies can also appear over a much larger area (the alteration zone) since the formation of deposits often can spread traces of metal a considerable distance.

Following the analysis of geologic, geophysical and geochemical data, the most promising anomalies can be further evaluated with rock sampling and trenching. These techniques allow geologists to evaluate surface targets in two dimensions. If the results warrant further testing, diamond drilling follows. Magnus International Resources' typically contracts a diamond drilling company to undertake this phase of exploration.

A diamond drill cuts and extracts a continuous cylindrical core of rock, providing a third dimension to previous testing. The diamond drill's rotating core barrel has a diamond "bit" attached to the cutting end that grinds into the rock formation. Hydraulic pressure forces the rods downward as they rotate at high speed. Water pumped through the rods cools the bit and washes away rock cuttings. The drill core is placed in boxes or trays for logging and sampling. The exploration geologist then reviews the drill core, noting the rock type, colour, hardness and other characteristics. Sections of core with mineralization are split in half lengthwise. Half is returned to the core box; the other half is sent to an assay lab for analysis. If drilling has cut through a mineralized zone, additional drilling could determine the size and shape of any potential ore body. Calculations would then determine the tonnage and grade of the potential ore body. Tonnage equals the (length x width x thickness) x specific gravity of the mineralized zone.

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ENGINEERING

Mining engineers use this information to determine if the ore body contains enough ore at a high enough grade to make mining economically worthwhile. They need to assess the type of mine needed; the physical obstacles to getting to the ore; and what impact a mine would have on the area's wildlife and environment. If the ore body is close to the surface, the engineers will design an open-pit mine; if it is buried deeply, they will plan an underground mine.

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MINE BUILDING

Even if the ore body is close to the surface, extensive infrastructure is required. This makes mining a time-consuming process; it can take up to a year to build even the most basic open-pit mine. The length of time between discovering a mineral ore body and extracting it can be up to five years.

Because mines are often in remote locations, it's necessary to build roads, administrative offices, equipment storage areas – and even towns, schools and medical facilities. Mines must also proceed through a lengthy approval and permitting process at multiple levels of government. Mining companies must also set aside funds for land reclamation once mining is complete. Preparations for a modern mine can cost in the hundreds of millions of dollars.

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MINING AND PROCESSING

Part of determining whether an ore body can be mined economically is assessing the metallurgical quality of the mineralization to select the appropriate processing technique required to remove the metal from the ore. A mine site includes a processing area where the ore is crushed and undergoes various processes depending on the nature of the associated minerals and then the loose rock is sent to the appropriate processing location. Gold is a good example of the many options for processing. Low-grade gold ore is relatively simple: a cyanide solution is applied to the heap of crushed ore, dissolving the gold for collection. High-grade ore goes to a grinding mill for a more extensive process. Different ore types require different processes for optimal gold recovery:

• Oxide ore goes directly to the leaching circuit, where cyanide dissolves the gold.
  
• Refractory ore is roasted at 1000 degrees Fahrenheit to burn off the sulphide and carbon it contains before going for leaching.
  
• Sulphide refractory ore has no carbon and is oxidized in an autoclave to separate the sulphide from the ore in a safe, environmentally friendly way. The ore is then goes to the leaching circuit, where gold is extracted from the solution and deposited onto activated carbon. A chemical process strips out impure gold, which is then melted into doré bars. They are about 90 percent pure gold and are usually shipped to a refinery where they undergo further processing.

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REFINING

The refining process removes the remaining impurities from the gold, which is either recycled scrap being upgraded or gold destined to become bullion bars. The first step melts crude gold and treats it with chloride, converting remaining metals to chlorides that will drift off the gold. The resulting gold -- 99.5 percent pure -- is cast into electrodes known as anodes, which are put into an electrolytic cell. After a current passes through the cell, the end product is 99.99 percent pure gold.

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RECLAIMING THE LAND

When gold reserves in a mine are exhausted after a number of years, a reclamation project returns the land, as much as possible, to its previous natural state. The project follows the plan submitted to government authorities before the mine was built, which details the strict guidelines the company will follow, during the life of the mine and its closure, to protect wildlife and the surrounding environment. The reclamation project will include such things as planting trees and grass, and supporting the return of wildlife.

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