The modern gold mining techniques are quite efficient and economical. The use of gold and golden ornaments started several thousands of years ago and this metal was dug from the earth using crude tools and equipment.
Ever wondered how the lustrous gold metal was dug from the earth in the early days? Well, our ancestors never just relied on luck while digging gold or picking up gold pieces by the river. They had special techniques that they used to obtain gold. Some of the mining techniques used from the late 1800s included:
In Placer Mining only simple tools such as knives were used. There were also wooden tools such as shovels and picks that were employed. Dry-washing was a very popular method of placer mining. This method was inefficient and crude but was not expensive. Once gold-bearing gravel was dug, it was dried in the sun and then ground into dust. A pan was then used to throw the dust into the air repeatedly for the wind to blow away the fine dust particles and leave the heavier particles containing gold to settle in the pan. Water could also be used to wash away the fine dust particles and allow gold to settle down in the pan.
Hydraulic mining was widely used from 1853 to 1884. as the name suggests, water was the main agent used in this process. Water under high pressure was directed at the banks with the gold-containing gravel. This could loosen large volumes of gravel that could then be washed by hand. Riffle-sluices were used to recover the gold and mercury (quicksilver) was added to help recover as much gold as possible. This process resulted in huge deposits of debris that were not environmentally friendly. That's why, in 1884, a legal injunction was issued to stop this method of gold mining.
Pocket Mining/Tunnel Mining/Drift Mining
After some miners discovered that gold was present in some outcrops from buried river channels, they came up with the pocket, tunnel, and drift mining techniques to mine gold that was still buried underground. These methods were very expensive and were only economical if used on gravel that contained substantial amounts of gold. The gravel that was obtained was washed or milled severally because they were very hard.
Dredging is a gold mining technique that was used from 1897 to 1970s. In this method, several buckets were made to form a chain that was used to transport gravel and mud from the bottom of rivers and deposit them in sluice boxes. Screens were then used to separate the coarse materials from the fine materials and finally, mercury was used to separate the gold from the coarse materials. Steam was used to drive the dredging machine. The dredging method began in the 1850s but it took about 40 years for it to be developed to an extent that it could be used practically in the field.
Hard Rock/Quartz Mining
This mining technique was first used in 1849. it gained much prominence around 1852 after which it collapsed. 10 years later, it rose again and became the main gold mining method. It wasn't an easy journey to develop this mining method. Many economic, technological, and geological challenges had to be overcome. Initially, the technique was only used on shallow deposits but it was later developed to mine in deeper pits.
Crushing/Quartz Ore Mining Method
The crushing method employed a crushing device called arrastra. The device was essentially made of stones arranged in a circular pattern to hod the gold-bearing ore. A strong post was driven to the ground at the center. This pole acted as the pivot for another pole which was driven by a mule to pull a very heavy stone to crush the ore into a fine powder. Water and quicksand were added to form a suspension. Water then drained off leaving an amalgam of gold and quicksilver. This amalgam was panned to obtain gold.
Open Air Mining
Also known as open-pit mining, the method has been adopted as the best mining method, not only for gold but also for mining of other precious metals. It applies modern technology to carry out preliminary studies and analysis before coming up with detailed mapping of the areas with gold deposits accompanied by 3D computer modeling defining the core mining operations. In the mining process, concentric ledges or rings are used for excavation.
Most gold mining methods, especially those used in the 1800s, led to environmental degradation. The used of fuel-driven machinery also led to air and soil pollution. That's why many governments have been coming up with regulations to control this industry. Not only that, but the price of gold is also being controlled because many countries use gold to determine the values of their currencies.