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Mica mines mainly include biotite, phlogopite, muscovite, lepidolite, sericite, green mica, iron-lepidolite, etc. In actual industrial application, the lager the mica is, the higher the value is. So it is necessary to protect the mica crystals from damage during mining period.
The specific mining methods are divided into open-pit mining and underground mining. This post mainly introduces the mica open-pit and underground mining methods, development methods and mining process.
In the mica open-pit mine, the ore body is shallowly buried and the veins are small and scattered. In order to protect the mica crystals, when you start open pit mining, you’d better not use rake equipment in the stope face. The mining method should be kept as simple as possible. Most of the deposits use open-pit mining, whose industrial raw material mica reserves less than 200t.
At present, there is no clear standard for the division of the mining scale of mica ore deposits. Generally, the annual mining volume of large-scale mica mine is 60,000 to 100,000 tons, and the service life is between 10 to 6 years. The annual output of industrial raw material mica in large mines is 90-200t/a.
The development and transport mode of mica open-pit are mainly to build the transport roads between the ground and benches as well as benches between, in order to link up the open pit with the ore site, waste dump and industrial sites, and prepare new working levels in time.
There are 3 common development and transportation methods for mica open-pit mining:
①Highway development: When the produced quantity is small, 5t dump trucks are used for mica transportation in mines;
②Slope lifting development: This development method is suitable for short lifting distances of rocks. Mica rocks are often lifted by mine car;
③ Development without ditch: In some mining areas with high terrain difference and small surface boundary, in order to solve safety problems, the mine will use simple ropeways that across the stope to improve transportation.
The mica mine has a large mining area with small and scattered veins. The distribution of vein structures is intricate and complicated, either along the schistosity or along the joints. Generally, the utilization rate of mica crystals is low. In general, although there are many pegmatite veins in a same mine lot, rocks that meet the mining conditions are very limited.
The mining characteristics of mica open-pit mines depend on the nature of useful minerals. The shape and the usable area of the mica crystal is larger, the value is higher. Mica open-pit mine is often mined in a small scale and simple technology. The common mining method is to transport the surrounding rock to the waste rock yard.
In order to reduce mica loss that caused by the crystal damage, you can choose 01-30 hand-held rock drills, and a down-the-hole drill with a hole diameter of 80mm or 100mm to do the drilling and blasting. When placing the blast holes, you need to avoid the mica rich ore zone.
The mining depth of the mica open-pit mine is generally 100 m. when the depth is as deep as 100 meters, you can increase the yield and the production capacity of the open cast mine, expand the mining work line, and further reduce the mica loss of the waste rock yard.
After the blasting, the mica ore is picked manually on the mine face.
The mine face generally uses a 0.5m3 bucket capacity excavator and a 5t dump truck to load the ore and transport it to the rock dump.
Mica underground mining, like other minerals, mainly is digging a series of tunnels underneath which are leading directly to the ore body.
In practice, the widely used mica underground mining methods are horizontal layered filling mining and ore retention, stage forced caving and stage mine combined mining.
Mica underground mining, like other minerals, is digging a series of tunnels underneath which are leading directly to the ore body.
In actual practice, there are 5 methods widely used in mica underground mining. Such as Horizontal layered filling mining and ore retention, stage forced caving, stage mine combined mining.
Because the topography and occurrence conditions of the deposit vary greatly and complex, there are many ways of underground developments.
The development and transportation in mica underground mines are inclined shaft development and adit development.
The adit development is the most economical and ideal method for mica mine development. Its advantages are as following:
① Based on excavating the roadway along the vein, it can play a supplementary role in prospecting by combining production exploration, development and mining standard;
② Due to the small tunneling workload, the mine can be put into production quickly;
③ The mined ore can be offset-part of the development cost;
④ It can reduce the transportation and drainage costs.
When the adit development limited by the topographical, you can choose inclined shaft development. Its advantages are roughly the same as those of adit development:
① The excavation workload is small；
② Mine can put in to production quickly；
③ The costs for transportation and drainage can be reduced.
Compared with other non-metallic minerals, mica underground mining has its particularity. Because the ore and surrounding rock are hard and stable, you can stope and process mica in the mining face. There are some common mica underground mining methods: shrinkage method, filling method and room and pillar method.
The entire underground mining is carried out in layers from bottom to top, with a height of 1.8-2 meters. After blasting, the falling ore will fall onto the previously mined filling layer. You can hand-select large mica crystals from the collapsed ore directly. The waste rock can fill the mine-out area.
The +100mm-sized rock blocks are manually piled into a rock wall which can stock the rock fragments. The -100 mm fragments containing small mica crystals are placed on the chute, then they are sent to the ground for the recovery of mica.
When mining the stable giant crystal mica zones which near the roof, you need to drill a hole 03-0.6m away from the ore body, then charge and blast. In order to protect the form of mica crystal, the blasting process just used to loosen the mica tape. Therefore, the blast hole is generally set at the lower part of the giant crystal mica zones and filled with a small amount of explosive. After blasting, you need to pry off the mica with the bit.
For discontinuous disseminated underground ore bodies, the position of the blast hole is determined by the mica distribution law of the mining face. When the rock drill reaches a certain depth, you cannot continue drilling. Meanwhile, you should consider whether the blast hole is charged or not according to the actual situation.
In short, the mica underground mining technology is drilling, blasting, manual transportation to the outgoing patio, manual filling, and patio leakage transportation.
The above is brief introduction of mica open-pit mine and underground mine mining process. In order to increase the mining recovery rate and ensure the safe production of the mine, in actual mining, you need to fully explore the mine and select the appropriate mining method and technology for mining based on the mine geology report.
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