Gold is a dense, soft, malleable, and ductile metal. It has an attractive bright yellow colour and luster that doesn’t tarnish or rust in air or water. It is a chemical element with the symbol Au and atomic number 79. Gold is one of the least reactive chemical elements and remains solid under standard conditions. The metal often occurs in free elemental form, as nuggets or grains in rocks, in veins and in muddy deposits. It less commonly occurs in minerals as gold compounds, such as with tellurium as calaverite, sylvanite and krennerite. This metal is very valuable and has been a highly desirable and precious metal used for coinage, jewelry, and other arts since long before the beginning of recorded history.
Gold can be found close to the surface of the earth as well as underground mixed with other metals such as copper, silver and lead. Where the gold is found will establish what type of mining process is used to retrieve it. By studying the type of formation of certain rocks in a region and taking samples geologists direct where mining companies will need to explore. To determine what exactly is at a sight they will need to take numerous ore samples using the diamond core drilling method, the drills that are used are coated with industrial diamonds at the tips. By examining the samples carefully, geologists can tell engineers exactly where the ore they want is located and how it is combined with other metals and rock.
The two main gold mining methods are “Placer mining” and “Vein Mining”. Placer mining is practiced when the metal is found in loose deposits of sand and gravel from which the gold can be easily separated because of its high density. The concept is that the gold in sand or soil will settle to the bottom because gold is heavy/dense, and dirt, sand and rock will wash away, leaving the gold behind. There are certain different techniques used for placer mining such as panning, using a sluice box, hydraulic mining and dredging. Each of these methods involves washing sand, gravel and dirt in water. Gold then settles to the bottom of the pan, or into the bottom of the riffles of the sluice box. The gold dredge is the same concept but on a much larger scale.
Vein, or lode mining is the most important of gold recovery methods. Each ounce of gold recovered requires the processing of about 100,000 ounces of ore. Much gold is deposited in rock veins and this method accounts for more than half the world's total gold production. Gold in veins may be of microscopic particle size, in nuggets or sheets, or in gold compounds. The ore requires extensive extraction and refining.
To isolate pure gold, mining companies use a complex extraction process. The first step is to break down large chunks of rock into smaller pieces using large machines known as crushers. This will reduce the ore to be no larger than road gravel. This material then enters rotating drums filled with steel balls. In these drums, the ore is crushed to a fine slurry or powder....