Technological process in the Roşia Montană Project
Documents: Technological Processes
1 Set up of pits
- 4 pits will be set up: Cetate, Carnic, Jig and Orlea
- The 4 pits will be mined in two stages: Cetate and Carnic during the first 9 years, whereas the pits from Orlea and Jig will be open after the 9th year, and the mining in Cetate pit will continue. Ore mining in the pits will be carried out until year 14.
- The closure of the pits and stockpiles will take place gradually, with Cetate stockpile as of year 5, the stockpile and pit of Carnic as of year 9, and Orlea and Jig pits during years 12 – 14.
- Special technology will be used for every area to reduce the impact on the inhabited and/or protected areas.
- As pit mining approaches the inhabited and/or protected areas, the quantity of explosive used for de-rocking will be reduced, in order to reduce the impact of vibrations and noise.
3 Loading and transportation
- The ore will be transported from the pits using trucks with a capacity of 150 tons.
- Transportation is made to the Process Plant or for final storage in stockpiles.
- During the final period of the project, ore will be transported to backfill the pits.
- The extracted ore is crushed (broken) before entering the grinding circuit.
- During this stage, the wet grinding of ore takes place in two types of mills, i.e. ball mills and semi-autogenous mill.
- Mills are shaped as cylinders rotating around the axis, with balls located in these cylinders to crush the ore.
- The ore thus ground is introduced in tanks, together with a sodium cyanide solution (CN).
- The leaching process takes place here, meaning the dissolution of gold and silver from the ore.
7 Gold and silver recovery on activated charcoal
- The sodium cyanide, which bound to gold and silver, is fixed in the pores of the charcoal floating in the solution inside the leaching tanks.
- The charcoal is recovered, while the gold and silver sludge is washed off from the pores using hydrochloric acid.
- Gold and silver recovery from the gold bearing sludge is achieved by electrolysis.
- The dóre alloy is poured in ingots in an electric oven.
- The alloy contains around 55% gold, the rest being silver.
10 Cyanide neutralization
- Sodium cyanide is neutralized before leaving the plant.
- This is achieved by an oxidation procedure (INCO). As a result of the process, the concentration of sodium cyanide is reduced below the maximum limit imposed by the Romanian and EU legislation.
11 Final tailings storage
- After cyanide neutralization, the tailings will be stored in a tailings management facility, behind a dam made of rock.
- This dam is designed to withstand an earthquake of magnitude 8 on the Richter scale and retain two consecutive maximum probable precipitations.
- The probability that this phenomenon appears within 24 hours is 1 in 100 million years.