We Went Down into the Pit of the Cukaru Peki Mine – What Is the Paste Fill, the First Such Facility in Serbia, and How to Reach Gold and Copper?

For the first time since it started operating, in December 2018, the Cukaru Peki mine, owned by Serbia Zijin Mining, opened its door to the media. Numerous media teams went to Bor in order to make sure that a miner’s job is not easy at all – however, the modern technology of the exploitation of the ores of copper, gold and other metals in this location has been raised to another level.

– The construction of the infrastructure took about three years, and the production started less than two years ago. In five years, we have gone from zero to a fully functioning mine. In addition to the modern technology and standards, we have implemented the full monitoring of water, land, air and noise – Dalibor Stojadinovic, the manager of the mine, told the gathered journalists, who went over 500 meters below the ground.

The exploitation of the ore body is carried out in three zones. The first zone is uncovered using the method of horizontal belts, the second zone uses the method of horizontal belts combined with open cuts, whereas the third one entails level mining.



– In all three cases, after the ore is excavated, the uncovered space is filled, thereby protecting the terrain surface from the disposal of excessive waste rock and the degradation of the terrain surface itself – Stojadinovic notes.

After the ore is excavated from the pit, it is transported and broken up into smaller chunks, after which it is transported by a system of transportation belts to the grinding system in the flotation. It is then ground and goes through the flotation process, whereby the final product is obtained – the copper and gold concentrate.

– Currently, the lowest cote is at an altitude of 260 m, whereas the final depth of the mine and the exploitation is 440 meters – our interviewee adds.

The pit is covered by video surveillance, so each process is monitored in the control room. The traffic is regulated by light signalization, and the entire mine is covered by 4G internet, mobile telephony, as well as landline telephony. While walking down the concrete-covered tunnels, you have the feeling like you’re in an open space, because great attention has been paid to the ventilation system.

The company has developed the system of quick copper flotation and selection by itself

An internationally advanced SAB system for grinding and meshing is located on the surface, and when it comes to the flotation system, the company has developed the system of quick copper flotation and selection by itself.

Mladen Nikolic, a mining engineer working as a technologist for the processing of minerals, explains what the flotation system is:

– The grinding facility works with two systems: directly from the pit through a belt transporter, and the second system goes directly from the ore disposal site, where it is transported by trucks to the unloading mesh. The primarily ground 160-mm ore is moved by belt transporters to the grinding facility. In the first stadium, the ore is ground and placed, after that, the product of the placing is transported to the flotation machine, where the flotation of the copper and pyrite mineral concentrate is done.



He adds that the concentrate itself is further sent to the filtering facility. With the help of thickeners and pumps, it is delivered to the filtering presses, where a further drying produces the definitive copper concentrate. The same applies to the pyrite concentrate, except that it is sent to its own disposal site.

The capacity of this facility is 20,000 tons a day.

Unique in Serbia and the region as well – paste fill

The paste fill is the fist facility of its kind since the beginning of mining in Serbia.

– Our job is to take the waste rock from the mineral processing facility. We mix it with cement, water and send this mixture through the boreholes to the pit, filling out the spaces which our colleagues excavated through their mining activities – explains Nebojsa Budjelan, a mining engineer working as the engineer on the jobs of preparing the paste fill.



The facility consists of a deep conical thickener (whose function it is to separate water from waste rock), with a diameter of 20 meters, a height of 20 meters and a total volume of around 6,000 cubic meters. There are also two silos for waste rock, with a capacity of 1,200 cubic meters each, and three silos for cement, with a capacity of 400 cubic meters each.

– The total cement consumption is 22 to 25 tons an hour, depending on which part of the excavated chamber we are filling out. We fill out from the –37 horizon, we are at the +390 cote here, so it’s some 430 meters underground – our interviewee adds.

On average, 55,000 cubic meters are filled out a month, and the aim is 63,000.

He points out that the entire process of the pasta fill facility is monitored from the central control room.

How to reach the gold?

“Laboratory Testing” of Serbia Zijin Mining is one of the company’s most recent facilities. It was put into operation this year and it has state-of-the-art instruments and the most modern technologies necessary for the analyses which are required from it.

One of the processes carried out here is the assessment of the gold in the concentrate.

– We are here in front of the room where our powdered samples are mixed with certain reagents and then further melted at a temperature of over 1,000 degrees in magnesium pots, which are temperature-resistant, in order to finally get a small pearl which consists of noble metals.



Then, in the dissolution process, we remove silver from the pearl, leaving us with a tiny grain of pure gold, which is further measured gravimetrically. We have sensitive scales which can detect masses that low and finally, based on that gold mass in the sample, we can determine the percentage of gold in the concentrate we are testing – explains Ivana Mitrovic, the deputy supervisor of the Center for Chemical Testing.

Aleksandra Kekic

Serbia Zijin Mining d.o.o. Bor

Zijin Mining

Dalibor Stojadinović

Mladen Nikolić

Nebojša Buđelan

Ivana Mitrović

Cukaru Peki

Cukaru Peki mine

copper exploitation

gold exploitation

exploitation of metals

SAB system for gridnign and meshing

ore grinding

ore meshing

ore flotation

fast flotation system

copper selection system

paste fill