gold panning

environmental impact

The industrial exploitation of the gold ore is an activity often highly polluting and contaminating the environment sustainably, even in Europe where this activity is not very known public1. In intensive farms golden soil and alluvium, as practiced in situ in tropical forests, the miners must merge the particles, dust or tiny sequins, using mercury, which is then extracted by heating and evaporation .

 These miners could still recover with a simple mercury evaporated, but they do it very rarely, and their entire mercury pollutes the environment. In ramps or "sluices", the very fine gold particles are brought into contact with mercury (the cleats of ramp) to amalgamate together. Some of this mercury is washed away with sterile or absorbed on organic matter and goes directly into rivers. The first by mercury poisoning are the miners who breathe the fumes when they distill. The rest of the mercury pollutes the air and the mist, dew and rain, soil and food chain (fish and shellfish in particular). Where ( in France) the amateur miners seek only sequins and gems, they have no need for mercury or cyanide.

Mercury is toxic (like all heavy metals), even at low doses and in all its forms. Note however that between sustainable food chains as its methylated form (methylmercury), the most toxic, produced by bacteria in anoxic conditions (standing water, sediment ...). This is a major pollutant of the environment, and one of those whose levels increase alarmingly in all compartments of the ecosystem. In areas where it is extensively practiced, gold mining is the main source. Mercury can be recovered by simple condensation, but this is rarely the case in the field.

• The techniques are also industrial waste polluting because they produce cyanide.
• On the other hand the use of pumps and powerful jets of water to disintegrate the soil and reduce mud that is mixed with mercury to extract gold is a source of pollution of soil destruction, by increased turbidity of the water, and the suspension of heavy metals or minerals naturally present undesirable but normally fixed in soils. 

In French Guiana, the soil is naturally rich in mercury (8 times more on average than European soil) increases this particular problem. In this case, even if the ban (effective since January 2006) was respected everywhere, use monitor nozzles would still be a source of significant pollution by mercury. Anaconda operations aim to fight against illegal mining.

Where can I find gold

Gold is found in gravel beaches, located in rivers. In these placer gold occurs as native particles are relatively big (millimeter flakes or nuggets) mixed sand and gravel.

The gold rivers comes from the disintegration of former mountain veins (veins detrital) in which he was to trace as veins of copper, iron, lead. Gold, because of its density, is also in pots that are rock crevices along the back of the riverbed.

Equipment for gold mining

To separate native gold alluvium, we use the gravity with the difference in density of alluvial gold (16 to 19 following the content of other metals such as silver or copper) sand (2).

Using different devices: The spray bar, or sluice Longtom is a channel made ​​of wood or metal, filled with carpets and special cleats which is caused to flow alluvium with a water stream. Gold is trapped or retained by the carpet behind the cleats while the sand is removed.

The trailing suction hopper dredger or "suction dredge" uses a pump to the alluvium in the riverbed or river, and pour on a spray bar placed on a raft.

There is a contemporary gold rush in French Guiana (overseas department (DOM) French), Brazil and Africa. In these countries, to recover gold, usually present only in tiny sequins and low in the alluvium of the major rivers, using barges and huge sucking the gravel with sucking in "sluices"

In France we use also of (small) suction dredgers but they are very common and its use is regulated, and any use of pump.

In France it also recovers gold by-product of sand.

• prospecting

It is the recognition and evaluation of economic placers. She is by techniques of hydrology and sedimentology and implementation of specific hardware.

• The technique of panning or pan

The pan is a pan that can separate the gold flakes in the sand. It is used to analyze the gold content of gravel and extract gold from concentrates obtained from carpets laid on a spray bar, a drag-suction or in a sand pit. The competitions are held washing gold on the dexterity of handling pans.

gold panning

What is gold panning? 

 Panning for gold is the traditional exploitation of alluvial gold, or rather the search for gold in rivers. In Haute Savoie, it has been practiced for a long time. Known origin dates back to the Templars in 1100.

The equipment needed .

 The range of the prospector is essentially composed of a pan (It's sort of a Chinese hat in sheet), a sieve, a shovel, a bucket, to hold just the glitz and possibly a sluice (wash table).

gold panning

What principle is used ? 

The basic principle is to separate the gold from the rest gravel. To do this we use the large density difference between gold and the rest of alluvium. The density of gold is 19.3 against approximately 3 for sand. 

We must therefore raise the gravel sieved to recover the sand in the pan. Is immersed in the water pan and is executed quickly oscillatory motion. The water gradually leads out of the pan all the light materials. Only remain at the bottom heavy elements: iron, magnetite ... and any gold flakes! Gravel digging is also high in the river on the banks height. The flakes do not move in case of high flood. So they are often deposited at a higher level of water in normal times. Note that gold is and always appears bright stainless. Sometimes the flakes are simply covered with limestone which starts very easily. No chemicals are used. The sorting is done manually and glitter without mercury. Another common technique is to place a wash table directly into the rivers. Gravel is thrown on the table equipped with cleats, grooves or carpet. These elements have the role of trap leaving only the glitter escape the sand and gravel driven by water power. Once as a carpet, were used sheepskins. Sometimes just lying in the bottom of a river. These skins, after several passages of floods, were removed to recover the glitter "trapped" in their fleeces.

What rivers in search of gold? 

 In France there are many rivers gold. Haute-Savoie is found in Cheran, the Arve, the Usses in some streams etc ... Otherwise in the Ardeche, the Gave (Pyrenees), Let Ales in the Cevennes, the Doubs, the Rhone and many more ...

Cheran 

Cheran is a beautiful river which rises to 2163 m altitude in the Bauges (Regional Park) in Savoy, and empties into the Fier Rumilly in Haute-Savoie. It runs 50.8 km through more than 20 different municipalities. Its most spectacular and wild, is located on any portion Cusy between Marigny and St. Marcel. From there, its course is lost in the depths of a meandering corridor sometimes very narrow and towering cliffs. No hydroelectric dam, no pipe, no systematic pollution of large plants can disturb its balance. 

Where is this gold? 

 The alluvial gold of Cheran's Alpine home. It would have been extracted from the rock by erosion of glaciers now extinct, which covered the Bauges. The rare native gold veins were then scattered in very large quantities of moraines. Over time, all the light minerals has been removed or washed away by rivers or eroded. The gold, much heavier, has remained focused and made the deposits rich enough to make them usable. This notion Agreements dated nineteenth century. Even today, geologists suggest several different assumptions

The United States, what about the gold rush?

The United States is not to be overlooked in the production of precious metals and especially gold, they take second place on the amount provided annually in the global market. If at the time of the Gold Rush and the discovery of mines in California, the Americans were able to produce a large quantity of gold, it was not the case to the 80. The frenzy of researchers is a bit dull and the mines were exhausted. In 1995, the U.S. will re-emerge with about 350 tons of gold per year provided by new mines in Nevada. However, the great American continent does not stop the United States as there are other countries like Canada that happens to produce nearly 150 tons of gold annually. The large mines of Ontario and northwestern Quebec are not to be overlooked if one speaks of world production of gold. Finally, South America is no exception thanks to Brazil even if production does not reach a significant amount, with 75 tons per year, the mines of Morro Velho Mineracao placed South America in the rank major gold producers in the world.

gold rush

gold 

Of course the main question that we posed to a prospector for the amount of gold that harvest. If a river is gold, this does not mean that just dig randomly and orpailler. Gold occurs in concentration in a few places, depending on the flow of the river at times of floods and other unknown factors (!). Many hours spent on prospecting without satisfactory results.

When we find "the vein", you can expect to reap ten sequins on average per pan. These flakes are barely visible for the smaller and usually go up to 2 mm in diameter. It takes more than a thousand sequins to make a gram! Sometimes we find larger specimens but this is uncommon.

The largest nugget ever found in Cheran weighed 43.5 grams. Its discovery dates back to 1863 in Alby sur Cheran.

The index of purity of this gold is estimated at 975/980 for 1000 is 5.23 carats. That makes him one of the purest in the world. (965 p. In 1000 for Australia and 880 p. In 1000 for California.)