Location and History

Buryatzoloto (Irokinda and Zun-Holba mines)

Buryatzoloto comprises the underground gold mines of Irokinda and Zun-Holba in the Republic of Buryatia in the Russian Federation.

Irokinda is located in the Buryatia Republic, approximately 75 km from the town of Taksimo, where the Baikal- Amur railway station and airport are located. The mine is accessible from an all-season road. Production began in 1985.

Zun-Holba is also located in the Buryatia Republic, approximately 315 km from the village of Kultuk, which is on the Trans-Siberian railway, and 400 km from the city of Irkutsk. It is also accessible by an all-season road. Production began in 1986.

These assets were acquired by Nordgold in late 2008 as part of the controlling interest in High River Gold. Nordgold holds a 90.6% voting interest in Buryatzoloto.

In 2016, Buryatzoloto produced 97.7 thousand ounces of gold.

Gold production (koz)

2017 2016 2015 2014 2013 2012 2011 2010
75.9* 97.7 112.7 119.7 98.5 108.9 134.3 136.1
  • *due to lower grades from Irokinda mine following the completion of high grade Visokya and Veins 3 underground mines, and due to processing water supply issues experienced in Q1 2017.

Mineral Resources and Ore Reserves Summary (31 December 2017)

Category Ore (Kt) Grade (g/t) Au (Koz)
ZUN-HOLBA RESOURCES
Measured and Indicated 764 6.08 149
Inferred 1,573 9.64 487
Total (M+I+I) 2,337 8.47 637
ZUN-HOLBA RESERVES
Proven and Probable 1,513 5.78 281
IROKINDA RESOURCES
Measured and Indicated 9996.93223
Inferred 5818.45 158
Total (M+I+I) 1,580 7.49 380
IROKINDA RESERVES
Proven and Probable 1,3214.63197


For more information, please see Mineral Resources and Ore Reserves Press Release

Technology

The Irokinda and Zun-Holba mines are both relatively mature underground operations. Both contain a processing plants, each with crushing, grinding, gravity and flotation circuits. The Zun-Holba plant also contains a CIL circuit and related facilities. For processing, there are two crushing stages and two grinding stages using ball mills, followed by gravity separation, which produces concentrates for both the gravity and flotation circuits. The gravity circuit is used to recover free gold, after which smelting produces doré bars. Flotation is used to recover finer gold particles into a flotation concentrate. At the end of 2014, Buryatzoloto employed approximately 3,000 people.

Buryatzoloto
Buryatzoloto comprises the underground gold mines of Irokinda and Zun-Holba.
Milling and Classification
Ore is sourced from underground operations using conventional mining methods involving drilling and blasting, followed by load and haul to the run of mine (ROM) stockpiles where it is either directly fed to the primary crusher or stockpiled. The ore is crushed to a P80 15 mm using a two or three-stage crushing circuit with screening. The crushed material is then conveyed to a grinding circuit consisting of deferent size ball mills.
Gravity Circuit
Both Irokinda and Zun-Holba mines use a gravity circuit to recover free gold before ore is milled finer for floatation. Primary concentration takes place in a centrifugal concentrator followed by cleaning of concentrates using several stages of shaking tables. This allows the plant to produce a gravity concentrate ready for direct smelting. Gravity gold recovery account for up to 20% at Zun-Holba and 60% at Irokinda.
FLOTATION
Flotation is a method of separating minerals depending on their ability to attach to air bubbles. The flotation process consists of producing a mineral concentrate through the use of chemical conditioning agents followed by intense agitation and air-sparging of the agitated ore slurry to produce a mineral rich foam concentrate. At Zun-Holba and Irokinda after grinding and gravity recovery circuit all the ore goes to flotation. The flotation concentrates from the Irokinda is shipped to the CIP plant at the Zun-Holba mine for further treatment by cyanidation and sorption.
CYANIDE LEACHING AND SORPTION
At Zun-Holba mine flotation concentrate is carried out in a carbon in pulp (CIP) circuit. During the CIP or CIL stage, pulp flows through several tanks where sodium cyanide and oxygen have been added to dissolve gold into solution. In the absorption stage, this pulp flows through several tanks containing activated carbon. Gold then attaches onto the activated carbon, which is moved counter current to the pulp, while screens separate the barren pulp from the gold-loaded carbon.
Elution
The gold loaded carbon is removed and washed before undergoing desorption. Desorption is achieved by introducing the gold loaded carbon to a solution of sodium cyanide at a high temperature (>110°C) and pressure. This results in the reversal of the attachment process, with the gold detaching from the carbon back into solution. This produces a small volume of solution with a high gold concentration.
Electrowinning
The gold loaded eluate solution that emerges from the desorption process is passed through electrowinning cells, where gold is deposited onto the cells cathodes.
Smelting
The cathodes then undergo a smelting process, further refining the gold and leading to the eventual production of doré bars for transport to a refinery. Dore bar is an alloy of gold, silver, copper and other metals containing between 50%-90% gold.

2018 Deliveries

  • At Zun-Holba, transitioning of mining operations from Adit and Shaft levels to Zun-Holba Deeps continue in 2018.
  • Zun-Holba Deeps will commence ore production from first long-hole open stopes in 2018.
  • Processing is focused on improving mill availability, and implementation of a cyanide analyzer/controller system.
  • Exploration is focused in Zun-Holba Deeps.
  • At Irokinda, ramping up of ore production from the new Sluchaynaya underground mine is in progress, while the first mechanized access development of Vein Visokaya commenced in H2 2018.
  • Underground mine development is focused on accessing ore to match plant capacity.
  • Processing plant expansion to 420ktpa and refurbishment was completed, optimization focused on mill availability and overall recovery improvements are in progress.
  • Infill diamond drilling from underground has commenced at Medvezhaya; aligned with the Irokinda LoM development requirements.

CONTACTS

tel.+7 495 644 44 73

Irina Dormidontova

RECRUITMENT MANAGER
tel.+7 495 644 44 73

OLEG BAZALEEV

HEAD OF SUSTAINABLE DEVELOPMENT PROJECTS
tel.+7 495 644 4473 #707 6746