Gold washing

The gold washing is the research and the artisanal exploitation of the Or in the Rivière S.

Layers

Gold is in beaches of gravel S, located in the rivers. In these Placer S native gold is in the form of more or less large particles (millimetre-length spangles or nuggets) mixed with sand and the gravel.

The gold of the rivers comes from the disintegration of old seams of mountains (detrital seams) in which it was with the state of traces like seams of Cuivre, of Fer, of Plomb. Gold, because of its density, is also in pots which are the rock anfractuosities located at the bottom of the bed of the river.

Vocabulary

The mining code regards as mines the lodgings known to contain (inter alia) mercury, money, gold, platinum, metals of the mine of platinum. Therefore the alluvial lodgings of rivers, exploited in career, are called gold mines, and the alluvia extracted the ore.

Research

; The prospection : It is the recognition and the economic evaluation of the placers. It is done by techniques of Hydrologie and Sédimentologie and by implementation of material the specific. ; Technique of the jamb or the side: the jamb is a basin which makes it possible to separate the spangles from gold of sand. It is used to analyze the gold content of the gravel and to extract gold from the concentrates obtained starting from fitteds carpet posed on a spray bar, a dredger-suction dredger or in a sand pit. The competitions of gold washing take place on the dexterity of handling of the jambs.

The stock

To separate native gold from the alluvia, one uses gravity with the difference in density of alluvial gold (16 to 19 following content of other metals like the money or copper) of sand (2).

Various apparatuses are used: The bar spray , sluice or longtom is a channel out of wooden or metal, furnished with special carpets and cleats in which one makes run out the alluvia with a water current. Gold is trapped by the carpets or is retained behind the cleats whereas sand is evacuated.

The suction dredger or " suction dredge" use a pump to aspire the alluvia in the bed of the river or the rivers, and to pour them on a spray bar posed on a raft.

There is a gold rush contemporary in Guyana (DOM), in Brazil and in Africa. In these countries, to recover gold, generally present that in tiny spangles and with low content in the alluvia of the large rivers, one uses gigantic barges and one aspires the gravels with suction dredgers in " Sluices ",

In France one also makes use of (small) sucker dredgers but they are spread very little and the use is regulated by it, like any use of motor-driven pump. (see Legislation concerning gold washing in France)

In France one recovers also gold in by-product of the sand pits.

Environmental impact

In gold the intensive exploitations of the ground and alluvia, as practiced in the tropical forests, the gold washers must amalgamate the tiny spangles, using mercury, which is then extracted by heating and evaporation (Sublimation). These gold washers could with simple a Alambic recover evaporated mercury, but they very seldom do it, and the integrality of their mercury pollutes the environment. In the slopes or “sluices”, the very fine gold particles are put in contact with mercury (on the cleats at the end of the slope) to amalgamate together. Part of this mercury is carried with the deads or adsorbed on organic matter and finds itself directly in the rivers. The first poisoned by mercury are the gold washers who breathe the vapors of them when they distill it. The remainder of mercury pollutes the air then the Brume S, Rosée S and rains, the grounds and the Food chain (fish and shells in particular).
Where (in Metropolitan France for example), of the gold washers amateurs seek only spangles and nuggets, they need neither mercury, nor of Cyanure.

Mercury is toxic (like all heavy metals), even with low dose and in all its forms. However let us note that it enters durably the food chains only in its methylated form (Méthylmercure), most toxic, produced by Bactérie S in anoxyques conditions (stagnant water, Sédiment S.). It is polluting major of the environment, and one of those whose contents increase in an alarming way in all the compartments of the ecosystem. In the areas where it is abundantly practiced, gold washing is the independent source. Mercury can be recovered by simple condensation, but it is seldom the case on the ground.

the industrial techniques are also polluting because of the cyanide scrap which they produce.
In addition the use of pumps and powerful jets of water to disintegrate the grounds and to reduce them out of mud which one mixes with mercury to extract gold from it is source of a pollution by destruction of the ground, increase in the Turbidité of water, and by the setting in suspension of heavy metals or undesirable minerals naturally present, but normally fixed in the grounds.

In French Guiana, the ground naturally rich in mercury (8 times on average than a European ground) increases this problem particularly. In this case, even if prohibition (effective since January 2006) were respected everywhere, the use of the lances monitor would cause nevertheless important pollution by mercury. The operations Anaconda aim at fighting against the clandestine exploitations.

Impact on health

In addition to the indirect impacts mainly related to the food ingestion polluted by mercury, the people who breathe the mercury vapors are exposed to an acute or chronic intoxication (Hydrargyrisme). Mercury in the form of vapor passes very easily from the air inspired in blood.
the cyanide derivatives, other waste of semi-industrial gold washing or the gold mines are also very toxic products, for the man, the animal and the environment.

See too

French Guiana, the gold of shame , by Axel MAY, Editions Calmann-Levy (2007): inquire into the gold bearing activity in the greatest department of France

Internal bonds

External bonds

Guyana and gold washing: impacts of the search for gold in the greatest French department on http://guyaneetorpaillage.over-blog.com/

Manual on line of the Gold washing, Gold digger
gold washing semi industrial
Gold washing-Leisure in France: Places, legislation, material, information and images
Gold washing in Gard, cuts Europe
the French federation of Gold washing and Research (F.F.O.R.)

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