Our company's success depends on discovering additional mineral reserves. These natural resources are found, extracted, and processed over a period of years and the process inquires complex scientific, environmental, and social planning. The goal of Yazhou Huangjin is to develop a mining company that is safe, responsible for the environment, and socially conscious.
Exploration
The process of finding gold is technical, complex, and time-consuming. Only 10% of the world's gold deposits contain enough gold to mine, making it unlikely that any given discovery would result in the construction of a mine. This makes exploration time-consuming and costly. While there are two to four parts per billion concentrations of gold all over the planet, in order to be lucrative, we need to find locations with 2,000 to 3,000 parts per billion.
So where do our exploration teams find potential massive projects?
Prospecting is the first step to complete. But because gold veins are often only a few feet wide and curve with the shape of the Earth, it is quite challenging to identify an exploring location amid thousands of square kilometers of land. Naturally, it makes sense to begin in regions where gold is thought to be present, but there are roughly 900 such spots to pick from worldwide.
Although starting with less-explored locations is ideal, we also look for exploration partners and/or purchase junior mining firms to speed up the process.
Yazhou Huangjin uses several methods to reduce the size of land to explore:
- Assess the geology of the area;
- Examine the water's and soil's geochemistry;
- Order aerial geophysics surveys to measure the amount of electrical and magnetic current in the subsurface crust.
Drilling is carried out once a target region has been identified and geological, geophysical, and geochemical data suggest a strong probability of a deposit. We can examine the kind and quality of minerals in the ore thanks to drilling.
How many samples are required, though? Which way should we go? How far are they apart? What depth? These aspects need to be carefully considered because drilling costs per foot are high. Another method of sampling we use is trenching, which is done with backhoes or bulldozers and hugs the surface. Crews mark the precise location and depth of each sample taken as they dig. Following that, samples are sent to a recognized laboratory, which determines the kind of minerals and gold grade present.
When information from the lab is received, we add geologic, geochemical, and geophysical data to those findings. Understanding the local geology is essential to the process in terms of both the economy and the environment. Geology has an impact on mining, processing, and how we handle waste rock, tailings, and water. It is also a crucial component of programs for rehabilitation.
Modeling the Ore Body
Production geologists employ data from sampling, testing, mapping, and observation to ascertain the grade (amount of mineral) in the ore and to establish the most efficient and successful mining procedures. In the mining of gold and silver, the grade is expressed in grams per ton. A percentage represents the copper grade. Knowing the grade helps choose which rocks go to the processing plant and which go to the area where waste rocks are stored.
Mine engineers can select mining techniques, design blast patterns, design dig patterns, and maximize the safety and efficiency of production by using this data and sophisticated computer algorithms to more precisely identify the orebody. They can also choose how the ore should be processed. Drilling and sampling data are often used by geologists to locate moist areas. Both open pit and underground mines can experience serious water-related issues. If areas of high-water content can be avoided or planned for in advance, we can reduce safety risks, costs, and production interruptions.
Identifying and Addressing Consequences
Operating a mine presents unique social and environmental concerns. We must assess prospective development risks against the profitability of production, as well as the local income and employment it generates, in order to conduct our business responsibly. We work to engage and consult with communities and governments that host our operations, as well as other stakeholders, with respect and transparency throughout the mine lifecycle, from the earliest exploratory activities through closure. Our programs engage residents, uphold human rights, support local development goals, and reduce the adverse effects of our operations.
Designing and Building a Mine
Surface (open pit) and underground mine designs are the two main types used for mineral extraction.
Surface
Surface mines are created by drilling through the Earth's surface one layer at a time, and are typically favored if the ore body is relatively shallow and consistent. The last mine has a conical shape. Drilling holes in the ground and then filling them with explosives are our first steps. Large shovels and front-end loaders are used to load the rock into massive haul trucks after it has been fragmented by blasting. Waste rock is transported to a different location for storage while rock containing gold, copper, and other valuable minerals is carted away for processing. Later, waste rock areas are restored.
In order to keep the water level below the pit floor as we dig deeper, we must dewater the mine. We extract millions of liters of water per day from the hole. Much of it is recycled locally (to control dust, etc.). Extra water is cleansed before being redirected into surrounding lakes or rivers.
There is extensive observation in and around the open pit to keep a close eye on:
- Slope stability and settlement brought on by dehydration;
- Vibration, dust, and noise;
- Water levels and water quality, including groundwater and pit wall runoff
Underground
Deep within the Earth, metals or minerals are extracted via underground mines. We excavate a tunnel to reach the minerals when constructing an underground mine. This might be a spiraling downhill tunnel known as a decline or a straight vertical tunnel known as a shaft. We excavate additional tunnels to reach the ore from the shaft or decline.
In order to offer adequate ventilation and emergency exits, we also mine out tunnels. By drilling and blasting, we mine the ore bodies and the tunnels. The ore that has been broken up is then brought to the surface for processing. Waste rock can either be taken to the surface or left underground and utilized to fill voids.
The tunnels are supported to ensure their safety after all materials have been removed from the inside. Depending on how stable the ground is and how long the tunnel will be used, different types of ground support may be required. In order for engineers to build the mine for optimal safety and value, these factors are known in advance.
Rock bolts or split sets, which are inserted into drilled holes to provide pressure to the surrounding rock and maintain its integrity, can be used to provide ground support. Rock bolts are occasionally strengthened by the use of chemicals or grouts. Wire mesh is also put in place to prevent smaller rocks from falling.
More support is offered by spraying Shotcrete, a mortar and concrete mixture, at high pressure into the tunnels' walls and backs. We also backfill each stope with a cement mixture after we have finished mining it. The amount of equipment that may be utilized is restricted and there is a larger risk to safety with underground mining, but there is less environmental disruption.
Operating a Mine
We employ strict controls when running a mine to stop or lessen any negative effects on the environment. Our environmental management systems are created to ensure that all environmental factors, such as management, monitoring, upkeep, training, and action plans, are integrated into a larger framework and are a crucial element of mining operations.
Yazhou Huangjin conducts business in accordance with all applicable laws, rules, and other legal obligations. To give a set of acceptable performance requirements within a framework of continuous improvement, we also use an internal management system that incorporates a global set of performance standards.
Active collaboration with various partners is another essential component of Yazhou Huangjin's role as a pioneer in environmental management. Through collaboration, we can better understand our effects and design tools that will help us increase the value that can be derived from mining.
Ore Processing
Ore is moved by haul trucks from open pits or subterranean operations to processing facilities. It is possible to store some ores for later processing. Waste rock storage sites are used to store rock that is not profitable to mine. The processing technique is determined by the grade and kind of ore. The price and methods used to extract gold are also influenced by the geochemical composition of the ore, which includes its hardness, sulfur content, carbon content, and other minerals contained inside.
Processing Methods
The ore is processed using one of the following techniques, depending on the type of ore: We feed the ore into a sequence of crushers and grinding mills to reduce the size of the ore particles and expose the mineral. Additionally, water is added, causing the ore to become a slurry. This slurry is sent to leaching tanks where it is mixed with a mild cyanide solution to dissolve gold and silver. Up to 93% of the gold and 70% of the silver in the ore are extracted using this method. The solution is then given a dose of carbon granules. As the gold bonds to the carbon, it is drawn out of the solution. Then, by washing the carbon with a caustic cyanide solution, we "strip" the gold from it.
Later, the carbon is recycled. The gold-containing solution is then pumped through electro-winning cells, which use an electrical current to remove metals from the solution. Tailings are the remaining waste products from the processing of gold. Tailings must be disposed of safely for the environment because they contain trace levels of cyanide and other dangerous substances. Tailings dams, which are lined with impermeable layers, are used to hold the tailings. Despite the safe cyanide levels in the dam, precautions are taken to keep wildlife away from the structures.
The sediments sink to the bottom as the chemicals degrade over time, allowing the facility to reuse the water for processing. The gold is subsequently smelted, which causes it to melt in a furnace. Doré bars are then made by pouring the liquid gold into molds. These are unrefined gold bullion bars that can have anywhere between 60 and 95 % gold content. Finally, a refinery will be used to further convert the bars into pure gold.
Alternative Ore Processing
In some processing facilities, we employ alternate gold recovery techniques to meet varied ore properties or other needs. Refractory ore, for instance, is defined as having a high concentration of carbon or sulfide minerals (or both). The high sulfide minerals in refractory ore retain gold particles, making it harder for the cyanide to reach the gold and leach it. As a result, refractory ore defies conventional processing techniques.
Heating
Refractory ore must be exposed to high temperatures, high pressures, and/or oxygen in order to leach gold from it. Yazhou Huangjin uses either an autoclave or a roaster to treat refractory ore. Leaching takes place before an autoclave is utilized. The slurry is heated before being fed into an autoclave, which uses high-pressure steam, water, and oxygen to chemically oxidize the sulfide material. The slurry is then chilled before being re-injected into the leaching process. If the ore to be processed contains a significant quantity of organic carbon, a roaster, an extremely high-temperature oven, is a common substitute for an autoclave. Heat and air are used in roasting to burn organic carbon into fuel and remove sulfur from ore.
Heap Leaching
In heap leaching, crushed ore is dumped onto mounds called heaps, to which drip feeders are used to delivering a mild cyanide solution. In the cyanide solution, the gold dissolves. To ensure that no solution leaks into the environment, the entire heap leach area is lined with high-duty liners. The gold-cyanide solution is then transported to a recovery plant after being collected in ponds and ditches.
Flotation
Flotation is a technique for sorting minerals based on how well they adhere to air bubbles. By changing the chemicals, flotation can be applied to a wide range of materials. While the slurry is in little tanks called flotation cells, air bubbles are added to it. To help the process, we add various chemicals to the slurry. Froth is produced when the desired minerals cling to the bubbles and rise to the top. The froth that overflows from the tank is taken out and transported to the following stage of processing.
Gravity Circuit
Prior to being leached, coarse gold is recovered using a gravity circuit. Similar to gold panning, gravity circuits operate on the premise that coarse gold is heavier than other materials and will sink to the bottom where it may be collected (gold is 19.3 times heavier than an equal volume of water).
Closing and Reclaiming a Mine
Yazhou Huangjin is dedicated to leaving a lasting legacy for the areas in which we operate as well as the environment. This commitment includes, among other things, creating an integrated closure strategy that considers social and environmental concerns and restoring affected land for useful purposes once our mines shut down.
Prior to the start of operations at a new site, planning for closure and reclamation begins. This planning continues as the mine is being developed. In our exploratory efforts, we try to cause as little land damage as possible. All disturbed ground is reclaimed, with the exception of highways if the neighborhood or government desires to maintain them.
Environmental Closure
Throughout the mine's lifespan, disturbed land is gradually reclaimed. The approach to site closure and reclamation, including the costs, are consistently analyzed and reported at every stage of the mine lifecycle due to a system developed and implemented by our closure and reclamation technical team.
Yazhou Huangjin aims to adopt a novel scientific method to solve the mineral waste produced by the extraction of precious metals when creating and carrying out reclamation plans. At a number of our locations, we have developed processes that are now widely used as industry-proven methods for mine site closure and reclamation. All operations strive to strike a balance between post-mining useful land use and environmental solutions.
The impact of closure plans:
- Social closure and rehabilitation help to stabilize the location's structures over time;
- Any groundwater beneath the site and any water discharged from it must be of quality so as not to harm aquatic life or other users of the water resource;
- We gradually repair portions of disturbed land in the mining area in order to restore the environment for future uses like ranching, recreation, or the preservation of wildlife habitat, which has multiple benefits;
- Improves the overall appearance of the troubled areas;
- Creates a cover to improve erosion protection;
- Reduces silt loads to improve the quality of run-off water;
- Reduces dust.
Social Closure
Local communities may be significantly impacted by the closure of a mine. As a result, we consult with our stakeholders early on in the project's development to make sure the value generated by the mine operation is transformed into long-lasting initiatives for the communities. Sites must establish a procedure for routinely assessing and revising closure plans with outside stakeholders during the mine's lifespan.