Dry Mining
The usage of heavy equipment in auriferous mining depending on the area the mining is to be done is pretty limited due to the costs and investments as well as maintenance.
Basic principles of gravimetric separation and concentration of alluvial gold
This consists in separating mineralized particles of different specific weights, generally by the means of water or air current. In a paste or homogenous pulp of particles smaller than ½ inch for optimal recovery several aspects need to be taken into consideration:
- specific gravity
- size and shape of the particles
- type of material, existence of clay, amongst others
Types of gravimetric separators
Sluices. These are made out of wood, iron, fibreglass with structured frames. Its dimensions vary according to the work systems:
- Handmade: 0.85 x 4.50 x 0.15; riffles 3/8 inches to 0.30 meters
- Automatic: 2.85 x 7.00 x 0.30; riffles 1 inch to 0.30 meters
- % of pureness: 25 percent
- Pulp density: 25 percent
- Gravel density: 1,5 to 2,0
- Weight of auriferous gravel before being processed in sluice canal: 2,170 K/m3
- Weight of processed gravel greater then ½ inch: 1,953 K/m3
- Weight of processed gravel less then ½ inch: 2,035 K/m3
Advantages: the jobs of separation in sluices have the following advantages:
- minor supervision
- can work in volumes from 10 to 1,000 m3 per day
- initial costs are very low
- does not require maintenance
Disadvantages:
- Does not recover fine particle sheets of gold and between twenty to thirty percent is lost.
- It accumulates and clogs material that is not heavy, requires periodic control.
- For washing processes it requires a higher amount of water.
- Periodic changing of burlap.
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