The mining of diamonds is controlled by a few major mining companies, the most influential of which is De Beers. But this is not the condition with gemstones mining, which is usually worked by independent miners. Several different methods are used in gemstone mining, varying from native mining to highly technical gemstone mining methods.
Open cast mining
Open cast mining is one of the methods of gemstones mining, where the overlying minerals or rocks are removed to reach the gemstones-bearing rocks. The gemstones-bearing rocks are then washed by jets of water under high pressure to obtain the gems. These are then sent to treatment plants for further processing.
It is used to describe the mining method where gem-bearing rocks are exposed by digging horizontal terraces in circular formations. Blasting is conducted, post which the debris is washed to get the gemstones. Emerald mining in Columbia is done this way.
Tunnelling technique is used for gemstone mining when the gem-bearing rock is extremely close to the surface. A tunnel is made to reach the gem deposits and mining is done by blasting or by picking up individual rough gems.
Undersea or marine mining
Where there are marine deposits like the Namaqualand diamond deposits in West Africa, marine mining is conducted. This involves land reclamation or deep sea dredging.
A river either changes its course naturally or is made to change artificially by blocking the river at two ends and creating a canal. The rock bed is allowed to dry and then the gemstones are obtained. The KGK Group has investments in primary gemstone mining in South America and Africa – two emerald mines, a Paraiba mine and a rubellite mine. The group is committed to ethical sourcing and benefiting local communities.