Gold prospecting by pan

 

Since the 1990s, prospecting for gold and oil — or «mineral prospecting» — has become one of the most active economic areas. This frenetic activity is directly related to increasing demand from emerging market economies, like China, Brazil and, more traditionally, India, and that of Western economies, which consider gold a valuerefuge. This has led, given its rarity of less than 4 milligrams per tonne of rock, to extreme pressure on the planet Earth, affecting its sustainability. In short, the richer its inhabitants the greater the demand.

The search process and subsequent extraction is known as «mineral exploration», defined as «the part of Geology which is interested in the search for minerals, rocks and energy resources with economic potential». Within mineral exploration, the most historical, traditional and cheap method would be alluvial prospecting or «prospecting by pan». This method and the associated technique — «panning» — is directly concerned with finding and assessing heavy metal deposits that indicate the existence of placer or residual deposits, and thus indirectly with determining the location of mineral and, therefore, geochemical anomalies. This requires the sampling of rivers and streams, which can lead to source or primary deposits of all types of minerals or also show up other companion minerals known as indicators or pathfinders.

This technique, logically used in the early stages of exploration, is not only employed for gold but also for substances known in their raw form as heavy minerals of commercial interest, such as platinoids and gems in the broad sense, including diamonds and technological and strategic minerals like titanium, zirconium, hafnium, rare soils, tin, tungsten and niobium-tantalum, the latter mined as «coltan».

A pan is a simple, cheap, easily obtained and easy-to-use recipient shaped like a dish, pan, bowl or basin, without sensors or electronics, which in the 21st century remains the most effective and efficient tool in mineral exploration. Some of its forms, as can be seen in this book and the accompanying video, are the result of empirical knowledge, materials close to hand, and the intuitive application of fluid mechanics, which is to say fluvial dynamics. Gold pans are used by millions of people worldwide for subsistence artisanal or small-scale mining, and are typically used in the Western world in the pursuit of panning as a hobby or sport.

 

CHARACTERISTICS OF GOLD

 

Gold, chemical symbol Au, occupies position 79 on the periodic table, between platinum and mercury, and belongs to Group 11 together with copper and silver. It is a relatively soft metal, ductile and malleable, and a good conductor of heat and electricity. Both gold and the other two elements in Group 11 show little similarity to the alkaline metals of Group 1.

 

 

Gold is a fairly widespread chemical element in the earth’s crust but at very low concentrations, of around 4 mg/t (0.004 grams per tonne of rock). Comparing this to another element such as copper, the average content of the latter is 23,000 times that of gold at around 47 grams in each tonne of rock. This proportion is not consistent with their monetary values, as gold is only worth 3,200 times more than copper.