DESIGNING A NEW PLANT

The steps involved are:

• Obtain a representative sample.
• Prepare the sample.
• Mineralogical analysis.
• Metallurgical tests.
• Design a preliminary flowsheets,
• Economic evaluation.
• Take a decision.

2.1 O btain a representative sample.

It is very important obtain a representative sample from the ore body to be mined; a bad sample will give wrong results and the decision to be taken could be wrong. If there are several deposits very close, it’s necessary take sample from each one so that the metallurgist can work with them separately and later joint all the samples in only one. Minerals and host rocks usually have different behaviour during metallurgical tests. So it’s necessary evaluate each sample separately.

2.2 Prepare the sample.

Once obtained the sample, this will be processed in the metallurgical laboratory. Generally before coning and quartering must be crushed all the material minus 10 mesh (1.70 mm). If the sample is large the coning and quartering procedure will be used for blending, usually one-half or three-quarters of the sample is split out and reserved for future use. After homogenization, the coning and quartering will be done several times until reduce the weight to give enough sample for the metallurgical testwork program that comprises chemical analysis, mineralogical analysis, and metallurgical tests.

It’s very important take all the possible care so that each sample can be homogeneous and representative. Thus, laboratory work will be easy and will be possible obtain reproducible results during the testwork.

2.3 Mineralogical analysis.

With this kind of analysis it’s possible determine:

• Minerals in gangue and ore.
• The possibility of any interference in the metallurgical process.
• Free gold.
• Size of liberation knowing the size of minerals.

Previously, can be required carry out a screen analysis in order to find out the distribution of minerals in each fraction of size. Thus, the product obtained will be homogeneous in the microscope and the observation will be easy. This sample must be done with sample of head and later with the sample generated in grinding and final tails of each test.