4 Processes of Gold Mining You Need to Know (Ⅱ)

Gold mining refers to the process of mining ore from the earth's crust and enriching the minerals. From the previous article, we learned that the complete gold mining process mainly includes the following four aspects:

• Gold prospecting

• Gold mine design

• Gold mine production 

• Closure

The previous article introduced the first two processes of gold mining: gold prospecting and gold mine design, and this article will focus on the content of gold mine production and operation and closure.

Let’s drive in!

Gold mine production is an important stage for implementing the predictions and plans made in the first two processes into practice. The stage of gold mine production is: gold mining-gold beneficiation -gold smelting.

Gold Mining

Gold mining methods are mainly divided into two categories: open-pit mining and underground mining.

Open-Pit Gold Mining

In general, open-pit mining requires the following steps:

1. Ground cleaning: clear up various obstacles in the gold mining area.

2. Mine drainage: To those underground mines with underground water, a great deal underground water resource within a certain range must be discharged in advance and isolate the groundwater by interception to ensure the normal production of open-pit gold mines.

3. Gold mine capital construction: The construction work includes the excavation of main access and pioneer cut, planning of transportation routes, construction of the dump, industrial premises and hydropower facilities, etc., which are necessary work to ensure the production of the open-pit gold mining before it is put into production.

4. Stripping and mining: Stripping refers to the excavation of surrounding rock and topsoil to expose the gold ore body; mining refers to the mining of gold ore along with the stripping of rock and soil.

5. Ground restoration: Restore the land occupied by open-pit gold mining designedly.

Underground Gold Mining

In general, underground mining requires the following steps:

1. Tunnel development: Underground gold mining starts with digging some tunnels from the surface close to the ore body, which is the support system for the mining work such as transportation, ventilation, power supply, wind supply, water supply, drainage and filling.

2. Stope preparation and cutting: Stope preparation is the preparation work for transportation, rock drilling, ore drawing, ventilation, etc. in the ore block after the completion of the development project. Cutting is to open up a free surface and falling space in the ore block for gold mining after the completion of the stope preparation.

3. Stopping:Stopping includes three operations: ore drawing, ore transporting and ground pressure management. Underground gold mines mostly use rock drilling and blasting methods. Ore transporting is the transportation of ore from the mining site to the surface. Ground pressure management is a variety of technical measures taken to ensure the safety of the goaf.

Gold Beneficiation 

The content of mineral gold in the ore is low. It is necessary to crush and grind the ore and enrich it through beneficiation to separate the gold from the ore. Gold beneficiation process is mainly as follows: gold crushingand grinding – gold separation – gold tailing processing.

Gold Crushing and Grinding　

Gold ore crushing and grinding is to obtain the appropriate particle size suitable for the separation stage. The crushing and grinding process follows the principle of more crushing, less grinding, and segmented crushing, which effectively reduces the time and cost of gold grinding.

Gold Separation

Gold ore mainly adopts different beneficiation processes according to different ore compositions. The commonly used gold separation processes are gold cyanidation, gold flotation and gold gravity separation.

Gold Tailing Processing

There are several simple and feasible methods for gold tailings processing:

• Land reclamation, this method is suitable for valley-shaped gold tailings ponds.

• Organic waste is used to degradable solidify and seal the gold tailings dust. At the same time, suitable seeds and substrates are selected to promote plant germination and growth to achieve the purpose of vegetation utilization.

• Building materials. Brick is the most common building material, and the tailings can also be used to make flat glass and various heat preservation, sound insulation and heat insulation materials.

Gold Smelting

Gold concentrates need to be refined to become finished gold. Smelting refers to the use of roasting, smelting, electrolysis, and the use of chemicals to extract gold from the ore to reduce the impurities contained in the gold.

After the gold mine ceases operations due to factors such as exhaustion of the ore body or lack of mining benefits in the remaining reserves, the next focus will be on its shutdown and restoration. This is a complicated task. Gold mining companies have to safely shut down gold mines, and usually try to restore the mining area to the original environmental state. The focus of work will shift to decommissioning and ecological restoration of gold mine sites.

Decommissioning

During the closing phase of the gold mine, the gold mine infrastructure should be demolished and ecological reconstruction should be carried out to ensure that the mine is safe, stable and pollution-free after the mine is closed.

Ecological Restoration

Even after the gold mine is closed, the gold mining company still needs to be responsible for the management of the gold mine, usually for five to ten years or more. During this period of time, it is necessary to carry out ecological restoration of the goaf and dump.

Ecological Restoration of Gold Mine Goaf

According to the restoration goal of the gold mine goaf, it can be summarized into the following three modes.

• Agro-forestry model with agroforestry utilization as the goal of restoration.

• A water storage model aimed at the development of tourism, fishery, and sewage treatment ponds.

• A restoration model of natural vegetation restoration and artificially promoted vegetation restoration on the slopes of gold open pit mines.

Ecological Restoration of Gold Mine Dump

The ecological restoration of gold dumps is mainly based on agricultural and forestry utilization, and the vegetation restoration techniques used are:

• Stabilization technology of gold dumps. In order to ensure the stability of the gold mine dump, it is necessary to establish a complete drainage system; and establish a biological protection system on the slope of the gold mine dump.

• Soil improvement technology of gold dumps. Cover the surface of the dumping site with a layer of soil. The thickness of the covering layer depends on the nature of the underlying rock and the restoration purpose of the gold dump. Generally, the thickness is 10-60 cm, which is good for agricultural and forestry cultivation.

• Selection planting and allocation technology of plant seeds. Dibbling and sowing are generally adopted for planting trees and grasses in the gold dump. dibbling is planting with soil balls after digging holes or planting with nutrient soil.

The entire gold mining process is complex. The gold mine geological prospecting introduced in the previous article is tasked with providing geological data for the development of mineral resources; the mine design is for the planning and construction of gold mining projects. The gold mine production described in this article is an important process in the development of gold mines; the last gold mine closure is an indispensable process after mining companies complete gold mine production, which requires the decommissioning and restoration of gold mines. Every process is crucial.

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