Gemstone Mining Techniques

Gemstone Mining Techniques

By Engineer Clever Sithole

The mining techniques adopted to extract gemstones invariably reflect the nature of the deposit: primary deposits (in hard rocks, worked underground or in open pits) and secondary deposits (found in sedimentary, soft-rock, placers). The mineralogy of a gem dictates the type of geological environment in which it can be found. The necessary chemical ingredients, temperatures, and pressures were required in order to allow gems to grow. This means that the rocks and placers hosting gemiferous resources vary widely. Whereas important emerald sources all constitute primary deposits, ruby, sapphire, spinel, and other gems can often be found in secondary alluvial deposits. Considering that miners follow tectonic structures, the geology of gem deposits is central to subsequent extraction methods and intrinsic to the environmental consequences that can potentially arise. A notable difference between primary and secondary deposit is the use of explosives in the former but not the latter. This means that different regulatory approaches may be required.

A beautiful pair of earrings. A stunning necklace. A sparkling ring. Gemstone jewelry is a beloved accessory, and for a good reason: there is no simpler or more elegant way to add glitz and glamour to any outfit. Gemstone jewelry is also a must for special occasion presents, gifts, and proposals. But where do the gemstones come from?

Here, we go over how gems are mined through the different techniques of gemstone mining.

Underground Mining

Underground mining is typically the first method people think of when they hear “gemstone mining.” Just as you would imagine, underground mining involves digging below ground to reach ore deposits. Once the deposits are found, they are hauled back up to the surface for processing. The ore is then processed using heavy machinery, including crushers and grinding rolls. Workers must focus on ensuring all heavy equipment wear parts are in excellent working order to prevent accidents and downtime.

There are three major types of underground mining: tunneling, chambering, and block caving.

Tunneling: A technique often used to mine emeralds, this method involves locating a seam near the earth’s surface, creating a tunnel, and blasting or using a pickax to secure the deposit.

Chambering: A vertical shaft is drilled into rock surrounding a gem-rich vein; tunnels are drilled into the vein; and the gemstones are blasted out.

Block caving: This technique is often used to mine diamonds. Miners undermine a gem-bearing rock, which causes it to collapse under its weight. They then insert an undercut so that the rock falls and excavate the deposit from there.

Open Pit Mining

This gemstone mining technique is typically used to mine diamonds and a variety of colored gemstones. Open-pit diamond mines can be expansive, while mines for colored gems are usually much smaller in scale. Open pit, or open cast, mining is exactly what it sounds like: miners essentially dig a massive open pit. When the pit has been completely mined, it’s usually refilled and turned into a park, nature area, or even a suburb.

River Digging

Believe it or not, you can find an assortment of gems in rivers and lakes, depending on your location. Miners who dig in rivers and lakes use two techniques—wet digging and dry digging—to uncover gems such as opals, amethysts, garnets, rubies, and topaz. Wet digging is also known as panning, where miners collect sediment in a pan and shake it back and forth to separate the lighter and heavier materials. Dry digging is where lakes or rivers are blocked off and miners dig for gemstones in the dry beds.

Sea Mining

Some gemstones can be found on ocean beaches or deep in the sea. Deep sea mining is done by extracting gem deposits using a hydraulic suction system or a conveyor belt that runs from the bottom of the sea to the surface. Because these techniques are very expensive, they’re mostly used for mining diamonds. Interestingly, amber and pearl can be fished directly out of the sea using a net.

Eng. C. Sithole – GIA AJP/ GD, CPAA is an internationally accredited Gemologist & Mining Engineer trained at the Gemological Institute of America, World Gem Foundation (Spain), SSEF Swiss Gemmological Institute (Switzerland), HRD Antwerp Institute of Gemmology (Belgium), Indian Diamond Institute (Surat, India), European Gemmological Laboratory (EGL, South Africa), Certified Coloured Stones Grader & Pricing Specialist (Gem A, UK), Certified Pearl Specialist (CPAA, USA), GIA Accredited Jewelry Professional, Diamonds & Coloured Stones Graduate (GIA), B.Eng (Hons) in Mining & Mineral Processing Engineering (MSU). Currently, enrolled for an MSc in Mineral Resource Management with the University of Free State, SA.He represents DiamondMondaine (Belgium) as MD Mozambique & Zimbabwe


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