Placer deposits are the coastal sands, which are located along the shores of oceans, seas and rivers. The size of mineral particles is 0,07-0,2 mm (to 1 mm). Placers are occupied from hundreds of meters to tens of kilometers along the coast. The width of the placers is tens of meters (sometimes hundreds of meters). Seam Thickness is 2 meters (sometimes up to 10 meters).
Placer deposits are a traditional source of the production of zirconium, rare earth elements, titanium, tantalum, niobium, tin metals. Mining and processing of placer deposits are very developed throughout the world.
Today, due to the rapid development of technology, the extraction of marine placers is possible. There are special marine dredges. This is a very important point, because stocks of marine alluvial deposits are very large.
Placer deposits are a traditional source of the production of zirconium, rare earth elements, titanium, tantalum, niobium, tin metals. Mining and processing of placer deposits are very developed throughout the world.
Today, due to the rapid development of technology, the extraction of marine placers is possible. There are special marine dredges. This is a very important point, because stocks of marine alluvial deposits are very large.
In my opinion, the placer deposits can be considered as of the most promising feedstock for obtaining zirconium, rare earth elements, titanium, tantalum, niobium, tin metals.
Placers are the complex raw materials and they contain:
- Rare earth minerals (mainly monazite, xenotime and sometimes euxenite)
- Titanium minerals (ilmenite, rutile and leucoxene)
- Zirconium minerals (zircon)
- Tin minerals (cassiterite)
- Tantalum and niobium minerals (columbite, tantalite and euxenite).
To extract minerals from placers one can use environmentally friendly and cheaper technologies. Since the placers are small particles, there is no need to apply crushing and grinding.
Current and future processing schemes of placer minerals are included usually several ways of gravity separation of minerals to produce a collective concentrate (schlich, heavy concentrate). The tails of placer minerals don’t accumulate. The tails return to the ocean in a secure form (in the same form as the original raw material). Next may be used a combination of advanced methods of wet and dry separation of minerals. The schemes of ore processing may be different by sequence of operations depending on the mineral composition of placer. I would not recommended the use of flotation for the separation of placers due to the formation of harmful tailings. Today, there are environmentally friendly methods of mineral separation.
The processing of placer deposits has many advantages:
1. Processing of placer deposits is produced by environmentally friendly technology without the use of any chemicals. Virtually no negative impacts on the flora and fauna of the ocean and coastal areas.
2. Processing of placer deposits decreases the radiation background at the shores of seas and oceans. The ecological situation is improving becourse radioactive minerals are removed from the beaches. Beaches become a beautiful light color.
3. Good working conditions without dust and chemical vapours.
4. Perhaps the complex use of raw materials and the obtaining of several concentrates, which increases profit.
5. The use of cheap technology.
6. Low cost of search and exploration of placer deposits. One deposit can be used for long time. Ocean continuously feeds new portions of raw materials without a limit.
7. There are no the costs for the construction of the quarry or mine.
8. Low construction costs for the processing plant. One floating plant – the marine dredge can be used for 50 years and more at the numerous placer deposits.
9. There are no the costs of crushing and grinding.10. There are no the waste rock dumps, tailings containing hazardous and radioactive waste. There are no the costs for it.
11. There are no the costs of restoring the site.
12. Fresh water is not used. There are no the costs of preparation and purification of fresh water. Separation is made directly in seawater. Not any chemicals or minerals pollute the seawater.
Development of marine placers are very promising direction.
It is solution of tomorrow day.
However each placer deposit has its own individual characteristics.
Each ore must have its own individual technology.
© Ph.D. Natalia Petrovskaya
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