Gold Prospecting and Mineral Deposit Exploration

The objective of the mining investigation is that of providing to the world market the prime mineral or energetic minerals. The prospecting decisions of one or another mineral, in one place or another is in function of the economic and political context around the world and can be accomplished by the state or private organisms. In the first case the search of the prime materials is done by a public organism. In the second case there only intervenes the concept of revenues or utilities and the eventual search decisions are bound to the fluctuations of the world wide market. Another case can be given such as in the developing countries where prospecting can be trusted to a public organism in another country of another country, to a private society or international organism.  

Why to search for minerals
The increase of the needs is due to:

• An increase in the world population
• An increase in the needs of the population

This implies an increase in production or a relaunching of the investigations. However, the evolution of technology in addition creates new needs. For example, the appearance and start up of the motors of explosion and fuel derived from petroleum, has made necessary the creation of more resistant alloys that are possible with the increase of new mineral prospecting, such as antimony, chrome, nickel, cadmium, and the prospecting of petroleum. All of this implies the cycle of mineral economy. In the following we will give an example of the first mineral used by man, which is quartzite or flint. In origin, a prehistoric man, who was more observant than others, accidentally discovered the origins of the properties of quartzite and the advantages as far as the wood and the hardened clay in heat which were more hardness, a minimum amount of wearing down, sharp cutting edges etc.

After this:

• The first artisanal exploitation of mineral came about. Usage gave superiority over those that had wooden arms. 
• The commerce in change; with the increase of the demand the price increases.
• The protection of the deposit that brings about the envy of others: the owner protects his good and needs to do this by hand in order to do extraction and other thongs for the distribution feed. In this way we can see an embryo of a capitalist society show up (chief, worker, currency of change or buy, nations of a lot of work). Then competition shows up through “industrial spying” somebody obtains some flint and “prospects” the place. Another deposit is found, the prices become reduced, everything has its own variety of silica.

Sampling:

One of the most difficult tasks associated with placer mining is the sampling of the deposit. More placer projects have failed due to inaccurate assessment of the reserves than to any other reason. Within the realm of placers, those containing valuable minerals with a high unit value (gold) are more difficult to sample than those with larger bulk, lower unit value minerals (tin). Some items to consider when sampling a placer deposit are:

1. A relatively large size sample is needed for accurate valuation of the ground being tested. Placers are composed of many sizes of gravel that make a representative sample difficult to obtain.
2. When sampling placers for high unit value minerals such as gold, any error in mineral content of the sample will be magnified in the calculation of reserves.
3. Values usually are erratically distributed within the gravel mass. Therefore, some placers with a more uniform value distribution may be adequately assessed with a minimum number of samples, while a deposit with a high erratic distribution of values may not be adequately sampled regardless of how many samples are taken.
4. The investigation of a placer deposit should be made by or be under the direction of a person experienced in the art of placer sampling.
5. During a sampling program, items that must be observed and noted in addition to the sample size and valuable mineral content should include boulder size and number, clay content, bedrock conditions, water, frozen ground, false bedrock, and any other physical characteristics that would affect mining of the deposit.The steps to be followed in approaching a placer sampling program are outlined below:

– Reconnaissance: (1) check status of land ownership, (2) physical characteristics of area, and (3) research mining history of the area.

– Field inspection: (1) photogeomorphology, (2) surface grab sampling over all exposures of gravel, (3) few seismic cross section, (4) geobotanical study, and (5) survey for old workings.

– Choosing a Sampling Method: The main methods to consider are ( 1) existing exposures, (2) hand-dug pits or shafts, (3) backhoe trenches, (4) bulldozer trenches, (5) other machine-dug pits or shafts, (6) churn drill holes, (7) other drilling methods, or (8) bulk samples.

• Existing Exposures: If existing exposures are available, they can be tested for potentially valuable minerals by taking a grab sample and panning the sample. Advantages of taking samples from surface exposures are the low cost and the speed at which the samples can be taken. The disadvantages are that you can only sample what is on the surface and no quantitative information can be produced.