B08BCMH259 EBOK by Unknown

Author:Unknown
Language: eng
Format: azw3
Published: 2020-06-17T15:53:49.171000+00:00

concentrations might be high, the cost of separating gold from pyrite can be very high too. So, one always looks for ores that can be easily processed, and the desired element concentrated at a low cost. A typical gold ore process route is shown below.

FIGURE 12: Typical gold processing circuit using cyanide with carbon capture

If gold or copper can be heap leached, that is

thrown in a big pile and acid poured over it for a period of 3-12 months, and the gold or copper is dissolved passively as a pregnant solution; this is a low cost treatment method. However, this form of treatment also has lower recoveries than if you were to do an agitated or a tank leach. The capex is lower for heap leach, but the recoveries may not be as good as higher cost methods PILLAR 5: Mineral Economics | 47

such as tank leaching. So, the 3 critical factors affecting processing costs are:

1. The mineralogy of the ore.

2. How easy it is to remove the desired elements from the undesired ones.

3. The engineering, design and chemical treatment that is required to do this.

Many projects become economic when a new or

cheaper treatment method is established via test work, while other projects become sub-economic when it is found that conventional treatment methods do not work.

The Best Alternative to Wasting Money on New

Processing Methods

In general, one prefers to use ore treatment methods that are well established and have been in use for decades such as heap leach and electro-winning.

Engineers and investors are more comfortable with processing methods that are well established and have stood the test of time.

Typically, at this stage, laboratory scale and pilot test work are undertaken to design and propose a viable processing method.

Ideally, design templates adapted from other projects can be applied after test work confirms that the proposed processing method works.

In gold and copper processing, ores that are associated with oxides will require different treatment methods to those that are associated with sulphides.

48 | MINESTARTERS

For example, copper sulphide ores such as chal-copyrite often require floatation or specialized leaching conditions. In comparison oxides such as malachite require leaching in cold dilute sulphuric acid.

Experimental Processing: The World’s Worst Ever Mining Investment

If a particular element is tricky to liberate from the ore, and if the ore responds badly to established processing techniques, then a new mineral processing method may have to developed, or an established method will need to be adapted to treat this type of material.

However, this can turn out to be costly because the results are often unknown at the outset and the project becomes high risk.

Metal Price: The One Critical Factor that Affects All Mining Investments

The current metal price is the biggest single factor that will decide if a mine is economic or not.

For example, when gold prices are high, you can

mine low grade ore even at high cost. You can afford to strip large amounts of waste and still make a profit.

When gold prices are low, low grade ore becomes

sub-economic and therefore your cut-off grade rises.

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