Čoka Rakita Gold Recovery: Gravity & Flotation Processes

Source: Unnamed_Company_85 (2026)
Website: https://dpmmetals.com/assets/development/coka-rakita/

Critical Data

Overview

The Čoka Rakita Project, operated by DPM, is a high-grade gold skarn deposit located in Serbia. The proposed process plant, designed to treat 850,000 dry metric tonnes per annum, employs an integrated flowsheet comprising crushing, two-stage grinding, gravity concentration, and flotation to produce three saleable products: a flotation concentrate, a gravity concentrate, and doré bars. The feasibility study, updated in 2026, is based on extensive testwork by Wardell Armstrong and Base Metallurgical Laboratories, demonstrating overall gold recoveries exceeding 87%. The mineralisation is amenable to bulk sulphide flotation and gravity recovery, with coarse gold managed through a dedicated secondary gravity concentration circuit and direct smelting. Key equipment includes a refurbished AG mill and vertical stirred mill from the Ada Tepe mine, Jameson flotation cells, and plate-and-frame pressure filters. The plant achieves a target grind size of 80% passing 53 µm, enabling efficient liberation and recovery. Tailings are dewatered to 13% moisture for dry-stack storage or repulped with cement for paste backfill underground, supporting sustainable mine operations. The Čoka Rakita gold recovery process maximises value by converting a significant portion of gold into high-purity doré bars while generating clean concentrates for off-site sale. With a life of mine of 10 years and annual production peaking at over 260,000 ounces, the project represents a significant contribution to Serbia’s mining sector.

Key Process Stages

• Stage 1: Primary Crushing and Coarse Ore Storage – ROM material is fed via front-end loader to a vibrating grizzly feeder (64 mm openings). Oversize is crushed in a jaw crusher to 80% passing 92 mm. Undersize bypasses directly to the product conveyor. Crushed ore is conveyed to a 24-hour capacity coarse ore bin with mass-flow design to prevent freezing. Crushing operates only during the 12-hour day shift at a rate of 242.6 dry t/h nominal.
• Stage 2: Two-Stage Grinding Circuit – Primary grinding uses a 6.71 m diameter AG mill (3 MW installed) with a pebble crusher to handle critical size material, reducing ore to P80 212 µm. Secondary grinding employs a VTM-1250-WB vertical stirred mill (1,250 kW) to achieve the final product size of P80 53 µm. Each stage is closed by dedicated hydrocyclone clusters (508 mm and 254 mm cyclones respectively), with circulating loads of 146% and 188%. Water is added to maintain optimal slurry density.
• Stage 3: Gravity Concentration – A portion of the secondary cyclone underflow is screened on 1.83 m x 0.92 m scalping screens (+2 mm removed). Two parallel lines feed centrifugal concentrators (60–70 m³/h each). Primary gravity concentrate is collected in a holding tank then processed on a shaking table for 5 hours daily. Table concentrate (48 kg/t Au) is filtered, dried, and smelted into doré bars. Table tailings (1.5 kg/t Au) are dewatered, bagged, and sold as intermediate-grade gravity concentrate.
• Stage 4: Flotation Circuit – Overflow from secondary cyclones (27 wt% solids) enters a rougher conditioning tank with reagents (PAX, A3477, copper sulphate, MIBC). Rougher scalper Jameson cell (E3432/8) produces concentrate sent to the flotation thickener; its tailings feed a scavenger cell (same model). Scavenger concentrate goes to a cleaner conditioning tank then a cleaner Jameson cell (E1714/2). Cleaner concentrate combines with scalper concentrate to yield the final flotation product (65.5 g/t Au, 4.6% mass pull). Cleaner tailings recycle to the rougher recycle tank.
• Stage 5: Dewatering, Product Handling, and Tailings Disposal – Flotation concentrate is thickened in a 4 m diameter thickener, stored in an agitated tank, then filtered on a plate-and-frame press to 9% moisture. Filter cakes are stockpiled (7-day capacity) for blending and off-site dispatch. Flotation tailings are thickened in a 20 m thickener to 57% solids, then dewatered by two parallel plate-and-frame filters to 13% moisture. About 46% of filtered tailings are mixed with cement for paste backfill; the remainder is dry-stacked in a dedicated DTSF.

Additional Interesting Data and Summary

The Čoka Rakita process plant is designed for a 10-year life of mine with a nominal throughput of 850,000 dry tpa, achieving overall gold recoveries between 86.3% and 89.5% based on the production profile in Table 17.1. Gold production peaks in Year 3 at 263,559 ounces, with flotation concentrate contributing approximately 47% of total ounces, doré bars 25.5%, and gravity concentrate 15%. The process design criteria are based on the 85th percentile of ore hardness (Bond Ball Mill Work Index 13.7 kWh/t nominal, abrasion index 0.114 g). The comminution circuit leverages reused equipment from the Ada Tepe mine—an AG mill, pebble crusher, and a VTM—reducing capital expenditure and embodied carbon. The flotation circuit uses new Jameson cells (rougher scalper, scavenger, cleaner) selected for simplicity and cost advantages over conventional SFR cells. Reagent consumption includes 160–200 g/t PAX, 160–200 g/t A3477, 500 g/t copper sulphate, and 33–41 g/t MIBC. Environmental sustainability is addressed through a positive water balance (excess water treated before discharge), dry-stacked tailings management (54% of tailings), and paste backfill (46% of tailings with 5% cement binder) which reduces surface storage and provides underground support. The plant’s automation level allows manual and automatic control modes with online analysers for metal accounting. The total installed electrical load for surface facilities is 12 MW, supplied from the local grid. In the first month of operation, recoveries are expected to be 5% below design due to commissioning, normalising to within 0.4% of target by month 12. The feasibility study confirms that the Čoka Rakita gold recovery process is technically robust, economically viable, and designed for sustainable long-term operation.

Key Processes: Flotation, Cyanidation, Gravity Separation, SAG Mill, Ball Mill, Crushing

Target Commodities: Gold, Copper