How Is Silver Mined?

Silver is a shiny and lustrous metal with a long history of being used as currency and jewelry for its shine and beauty that can rival gold. This metal is found in the earth’s crust in its pure form as an alloy with other metals and minerals, and it has been mined since 500 BC; and from the mid-15th century, it was extracted in mass quantities due to the development of mining techniques. If you’re wondering how is silver mined, then we are about to break down the entire process.

Types of Silver Deposits

Silver deposits are naturally found in four forms in the earth’s crust, including:

1. Volcanogenic massive sulfide (VMS) deposit

These ore deposits are formed when magma from volcanic activity heats seawater and reacts with surrounding rocks to create a mineral solution that is deposited by rapidly cooling hot springs at the bottom of the sea to form volcanogenic massive sulfide deposits.

2. Sedimentary exhalative (SEDEX) deposit

These ore deposits are formed when the heat generated by the depth of deep sedimentary basins and water reservoirs causes minerals to precipitate due to chemical processes initiated by the heat to form SEDEX deposits.

3. Lithogene deposit

These deposits are formed when elements such as water wear down and carry minerals from solid rock to be redeposited elsewhere and form lithogene deposits.

4. Magmatic hydrothermal deposit

These deposits are found in a vein system as the hot water from magma intrusions in the crust rises towards the surface and precipitates silver minerals into veins forming magmatic-hydrothermal deposits.

Types of Silver Mines

Silver is mainly found in veins or nugget form, but the veins often break and scatter, which is why the mining sites must first be identified by using geographical maps and prospecting information based on evaluating the ideal environment for silver deposits. Once the location is identified, different mining techniques can be employed to extract the deposits depending on the depth of the vein, quantity of silver present, and rock types. The most common types of mines for extracting silver ore are:

1. Open-pit mines. These mines are close to the earth’s surface, and they are relatively cost-effective to construct depending on the depth of the mineral ores.
2. Underground mines. These mines are used to extract mineral ores embedded deep in the earth’s crust, and it requires extensive expenditure for setting up infrastructure to reach the metal.

Mining Techniques

Surface Mining

In surface mining, the soil and overlying rock materials are removed to extract mineral deposits, including:

1. Strip mining is used to excavate a seam of mineral, which in this case is silver, by removing a strip of soil and rock to reach the ore, and this method works best if the silver vein is found close to the surface.
2. Open-pit mining is used to extract minerals by removing them from an open pit, and this method is best suited to extracting vertical deposits of silver.
3. Mountain top mining requires removing entire mountaintops with explosives, and the metal ores contained in the rock are extracted with heavy machinery.
4. Placer mining requires looking for metal deposits and precious stones in river sediments, and this method uses river water to separate heavier elements such as silver from sand and mud.

Underground Mining

Underground mining or subsurface mining requires us to dig shafts below the earth’s surface and extract the metal from large pieces of solid rock. The extraction process begins with drilling blast holes into the rock parallel within the vein and parallel to the vein into the host rock or the rock adjacent to the vein. Once the blast holes are drilled, they are set with explosive charges such as dynamite that shatters the rock and bring it down into pieces. The pieces are either picked up by miners and loaded into minecarts or picked up by the scoops of load, haul, and dump machines, which are underground front-end loaders designed for hard rock mining. These machines are short, making it easy for them to enter the tunnels and they have a large bucket on the front to remove the rocks from the mine and take them to the surface. The metal ore is then dumped into trucks before it is transported to refineries for metal extraction.

By-Product Mining

Silver mining accounts for only 28% of silver extracted from the earth, while the remaining 72% comes from projects that produce silver as a byproduct of mining materials such as lead, copper, zinc, nickel, and platinum. Silver is widely available in nature, but the deposits are often too scattered, and it is often found with sulfides of other metals such as lead, copper, and zinc, making it a valuable byproduct.

Silver Ore Processing

Silver processing has several steps before the metal can be extracted in its pure form from the metal ore. Once the ore reaches the processing plant, it is crushed and broken up into smaller rock pieces to separate the silver particles from the non-silver particles physically. The rocks are crushed, and once the plant is ready to process the small pieces of ore, it is ground into a more refined material by running the material through ball mills until it takes a fine powder-like consistency.

The powder can then be separated using different techniques, including floatation and leaching. Flotation is a process in which the fine particles are mixed in water with air bubbles passing through the suspension. A low concentration of a hydrophobic chemical is added to the mixture, which attaches itself to silver particles and prevents them from attaching themselves to water molecules which allows normally heavy metals such as silver to float. The silver particles floating on the surface are removed from the top of the tank, and the floated concentrate is sent to be dried until it produces a silver concentrate.

In the leaching process, the powdered silver is dissolved by using cyanide as a leaching agent. The cyanide selectively leaches the silver; the material continues down to the leach tanks, and the remaining solids can be removed from the concentrate. The silver can then be extracted from the solution by using zinc dust which produces a silver residue that can be used to make dore bars.

Our Final Thoughts

Silver is a precious metal that can be mined close to the surface and at a depth through various methods, and it has the potential to be highly lucrative with discoveries of larger deposits and technological sophistication that improve mining practices.