Technical article on the GC processing plant flowsheet, equipment, and production performance at Silvercorp Metals Inc.’s Gaocheng silver-lead-zinc project in Guangdong Province, China.
The Gaocheng (GC) silver-lead-zinc project is an operating underground mine located in Yunfu City, Guangdong Province, China, that has been producing plant feed ore since Q2 2014. The project is 99 percent owned by Silvercorp Metals Inc. and processes polymetallic mesothermal vein infill mineralization containing silver, lead, and zinc for commercial extraction. The GC processing plant has a designed processing capacity of 528 thousand tonnes per annum (ktpa), equivalent to 1,600 tonnes per day (tpd), and was completed and commissioned in 2014. The plant sits on a steep hillside next to the main shaft, using the terrain to allow slurry to flow by gravity and reduce pumping costs. Construction timing for the existing operation is stated as 2014, while future expansion would depend on further study and permitting.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Designed processing capacity | 528 | ktpa | Equivalent to 1,600 tpd |
| Crushing product size (P80) | 15 | mm | Less than or equal to 15 mm |
| Grinding overflow fineness | 75 | µm | 80% passing (P80=75µm) |
| Grinding circuit concentration | 35 to 38 | % | Final overflow |
| Lead concentrate grade (historical) | 45 (about) | % Pb | Production records show 37–45% in 2022–2025 |
| Lead recovery (historical) | 90 (about) | % | Range 88.9–90.3% in 2022–2025 |
| Silver in lead concentrate | 1,500 (about) | g/t | Silver recovery ~60% |
| Zinc concentrate grade (historical) | 44 (about) | % Zn | Production records show 42–44% in 2022–2025 |
| Zinc recovery (historical) | 89 (about) | % | Range 89.5–91.0% in 2022–2025 |
| Silver in zinc concentrate | 290 (about) | g/t | Silver recovery ~23% |
| Sulphur concentrate grade | 45 (about) | % S | Sulphur recovery ~49% |
| Concentrate final moisture | 10 to 12 | % | After ceramic filter |
| Concentrate thickener discharge | 40 to 50 | % | First stage dewatering |
| Tailings thickener underflow | 72 | % | Concentration can reach more than 72% |
| TSF total design height | 99.5 | m | Elevation 233 m ASL |
| TSF total storage capacity | 2,989,300 | m³ | Design value |
| Current tailings stacking height | 71 | m | Elevation 204.5 m ASL |
| Tailings stacking volume to date | 1,356,000 | m³ | 45.4% of capacity |
| Remaining TSF capacity | 1,633,300 | m³ | Corresponds to ~2,858 kt |
| Pre-sorting discarding rate (2024) | 12.38 | % | From production records |
| Pre-sorting discarding rate (2025) | 16.66 | % | From production records |
| Water consumption | 5 | m³/t | Mainly from return water and mine water |
| Electricity consumption (2025) | 50.23 | kWh/t | From annual average |
| Steel ball consumption (2025) | 1.26 | kg/t | From annual average |
| Number of grinding-flotation lines | 2 | lines | Identical parallel circuits |
| Single line capacity | 800 | tpd | Each |
| Number of crushing production lines | 1 | line | Flexible operation |
| XRT sorting lines | 1 | line | Installed March 2023 |
| Tin recovery production lines | 1 | line | Gravity separation from tailings |
| Concentrate dewatering lines | 4 | lines | Lead, zinc, sulphur |
| Tailings dewatering line | 1 | line | Press filtration |
| Plant commissioning year | 2014 | year | Actual |
| XRT sorting commissioning | March 2023 | month-year | Trial production |
| Actual ore processing range | 260 to 630 | ktpa | Annual range stated |
| Lead content in lead concentrate | 5 to 6 | % | Approximate |
| Copper content in lead concentrate | 2 to 3 | % | Present |
Overview
The GC processing plant was designed by GDMAI with the preliminary design completed in April 2011. Construction finished in 2014. Depending on mining supply, one or two grinding and flotation lines can run. The actual annual ore processing volume has ranged between 260 kt and 630 kt. The plant uses a two-stage closed-circuit crushing process with a ROM feed size of up to 350 mm producing a product less than 15 mm. An XRT intelligent sorting system replaced manual hand-sorting in March 2023, with the system still undergoing optimization.
Historical production records from 2022 to 2025 show lead concentrate grading approximately 45 percent lead with about 90 percent recovery, containing roughly 1,500 g/t silver (about 60 percent silver recovery) and 6 percent zinc. Zinc concentrate grades approximately 44 percent zinc with about 89 percent zinc recovery, containing about 290 g/t silver (about 23 percent silver recovery). Sulphur concentrate grades about 45 percent sulphur with about 49 per cent recovery.
The processing flowsheet includes crushing and screening, XRT intelligent sorting, two-stage closed-circuit grinding and classification, lead preferential flotation, zinc-sulphur mixed flotation followed by zinc-sulphur separation flotation, tin recovery by gravity separation from tailings, concentrate thickening and filtering, tailings thickening and filtering, and dry-stacking tailings deposition. A regrinding-flotation test on lead concentrate has been proposed to reduce zinc content and produce copper concentrate.
Key Process Stages
Crushing and Screening. ROM ore enters a bin and is drawn by vibrating feeder into a primary jaw crusher. The jaw crusher product passes over a double-deck vibrating screen. Fines under 15 mm convey directly to the fine ore bin. Material over 60 mm feeds a secondary cone crusher via a buffer bin to maintain choke feeding. The 15 to 60 mm intermediate product goes to the XRT sorting system by belt conveyor. The crushing system typically operates at night during low electricity price periods, with peak versus valley prices differing by roughly double.
XRT Intelligent Ore Sorting. The XRT sorting system started trial production in March 2023. Intermediate screening product enters two-stage vibrating screens for washing. The washing pulp pumps to the grinding circuit. The oversize clean ore goes to the XRT machine for waste rock discarding. Waste rock is sold, and the concentrate returns to the secondary cone crusher buffer bin. The system remains under optimization to improve the tailings discarding rate.
Grinding and Classification. The grinding process uses two-stage closed circuit with grate ball mills and spiral classifiers in the first stage and overflow ball mills with hydrocyclone groups in the second stage. Final overflow fineness is P80 of 75 micrometres at 35 to 38 percent solids. Two parallel series each have a design capacity of 800 tpd.
Flotation. Hydrocyclone overflow goes to lead rougher conditioning with reagents and then to flotation cells. The lead circuit uses one roughing stage, two scavenging stages, and three cleaning stages to produce lead concentrate. Lead tailings flow to zinc-sulphur mixed flotation, which uses one roughing, two scavengings, and one cleaning to produce tailings and a bulk zinc-sulphur concentrate. That concentrate then enters zinc-sulphur separation flotation using one roughing, two scavengings, and three cleanings to simultaneously produce zinc concentrate and sulphur concentrate.
Concentrate Dewatering. Lead, zinc, and pyrite concentrates each use two-stage dewatering. First stage uses a thickener discharging at 40 to 50 percent solids. Second stage uses a ceramic filter achieving 10 to 12 percent final moisture. Dewatered concentrate is bagged and loaded into trucks by front-end loader for transport to smelter customers.
Tailings Handling. Tailings pump to a deep cone thickener for concentration. The underflow, which can reach over 72 percent solids, is valved either to the press filtration system or to the underground backfill system. Filtered tailings convey by belt to the dry-stacking tailings storage facility (TSF) and are spread by bulldozer on a bench-by-bench basis. The TSF is a third-class dam with displacement and phreatic line monitoring. The latest Safety Production Permit was obtained on August 31, 2023, valid until August 30, 2026.
Tin Recovery. An exploratory test on tin recovery from tailings achieved 34 percent recovery through gravity separation using shaking tables. The plant includes one production line for tin recovery from flotation tailings.
Laboratory and Maintenance. The GC processing plant is supported by an on-site laboratory, GC Laboratory, equipped with XRF, ICP-OES, AAS, infrared carbon and sulphur analyser, fire assay, and volumetric analysis rooms. It handles production samples, exploration samples, and conducts process tests. The maintenance workshop has craneage, welding, and basic machine shop capabilities. Major overhauls can be outsourced.
Additional Interesting Data and Summary
Production records from 2022 through 2025 show lead concentrate grades ranging from about 37 to 45 percent lead with lead recoveries of 89 to 90 percent. Lead concentrate contains roughly 1,500 g/t silver with approximately 60 percent silver recovery and also carries about 6 percent zinc. Zinc concentrate grades range from about 42 to 44 percent zinc with recoveries of 89 to 91 percent, containing roughly 290 g/t silver with about 23 percent silver recovery. Sulphur concentrate grade is approximately 45 percent sulphur with about 49 percent recovery. The copper content in the lead concentrate reaches 2 to 3 percent. The XRT intelligent pre-sorting system replaced manual hand-sorting in March 2023 and is still being optimized. Reagent consumptions for 2025 include ZnSO4 at 1.24 kg/t, CuSO4 at 124.79 g/t, and lime at 1.42 kg/t. Steel ball consumption in 2025 was 1.26 kg/t and electricity consumption was 50.23 kWh/t. Fresh water comes from the Hashui River via a riverside intake well and purification facility, while most process water is recycled return water and treated mine water. The remaining TSF capacity is about 1,633,300 m³ corresponding to roughly 2,858 kt at 1.75 t/m³ specific gravity.
Key Processes – Two-stage closed-circuit crushing (jaw crusher and cone crusher) with vibrating screen classification to minus 15 mm – XRT intelligent ore sorting for pre-concentration of 15–60 mm fraction, replacing manual hand-sorting – Two-stage closed-circuit grinding with grate ball mill and spiral classifier followed by overflow ball mill and hydrocyclone – Sequential preferential flotation: lead rougher-scavenger-cleaner circuit, followed by zinc-sulphur bulk flotation, then zinc-sulphur separation flotation – Two-stage concentrate dewatering using thickeners and ceramic disc filters to 10–12% moisture – Tailings dewatering via deep cone thickener and press filtration, with dry-stacking deposition at TSF – Tin recovery from tailings using gravity separation (shaking tables)
Source: Technical Report on Gaocheng Silver-Lead-Zinc Project in Guangdong Province, China, December 31, 2025. Project website: Gaocheng
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Technical Report on Gaocheng Silver-Lead-Zinc Project in Guangdong Province, China
The Gaocheng processing plant, designed for 528,000 tpa and operating since 2014, uses a flexible crushing and grinding circuit with lead, zinc, and sulphur flotation, plus integrated XRT ore sorting and dry tailings handling.
Report context
The Gaocheng Silver-Lead-Zinc Project is located in Yun'an District, Guangdong Province, China. The preliminary design for the mining and processing operation was completed by GDMAI in April 2011, and the processing plant was commissioned in 2014. The effective date of the technical report is 30 June 2024, with the report dated 20 July 2024.
Processing route
Crushing and screening
The plant uses a two-stage closed-circuit crushing process. Run-of-mine ore with a feed size of no more than 350 mm is drawn from a ROM bin by a vibrating feeder into a primary jaw crusher (PE600×900, 75 kW). The crusher product is screened on a double-deck heavy-duty circular vibrating screen (2YKR2460H, 45 kW). Fines of -15 mm are conveyed to a fine ore bin; +60 mm material feeds the secondary cone crusher (PYH-3Z, 220 kW) via a buffer storage bin; and 15–60 mm material is sent to the XRT intelligent sorting system.
Intelligent ore sorting
An X-ray intelligent sorting line (XRT intelligent sorting) was built and put into trial production in March 2023 to replace a previous hand-sorting operation. The 15–60 mm intermediate products enter two-stage vibrating screens (ZK2142) for washing; the pulp from washing is pumped to the grinding system. The oversize clean ore is distributed to the XRT sorting machine, which discards waste rock to a waste rock silo for sale, while the concentrate returns to the secondary cone crusher buffer bin. As of the report date, the pre-sorting feed size class remains under optimisation.
Grinding and classification
Grinding uses a two-stage closed circuit in two parallel series of 800 tpd each. The first stage is a grate ball mill (MQG2700×3000, 400 kW) with a spiral classifier, and the second stage is an overflow ball mill with a hydrocyclone group. Final overflow fineness is 80% passing 75 µm at a solids concentration of 35% to 38%.
Flotation
The flotation circuit is also configured in two parallel series. Lead flotation is one roughing, two scavengings, and three cleanings to produce lead concentrate. Lead tailings flow to zinc-sulphur mixed flotation (one roughing, two scavengings, one cleaning) producing tailings and a zinc-sulphur mix concentrate. This mix then undergoes zinc-sulphur separation (one roughing, two scavengings, three cleanings) to yield separate zinc and sulphur concentrates.
Concentrate dewatering
Lead, zinc, and sulphur concentrates each use a two-stage dewatering process: thickening to 40%–50% solids, then ceramic filtration to a final moisture content of 10%–12%. Dewatered concentrate is bagged and truck-loaded for smelter delivery.
Tailings handling
Tailings are pumped to a deep cone thickener for concentration, with underflow concentration exceeding 72%. The underflow is directed either to a press filtration system or a backfill system. Dry tailings are conveyed to a tailings storage facility and spread by bulldozer on a bench-by-bench basis.
Tin recovery
One production line recovers tin from flotation tailings by gravity separation.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Designed processing capacity | 528,000 tpa (1,600 tpd) | Design |
| Actual annual ore processing volume | 260–630 kt | Historical operating data |
| Grinding circuit capacity per line | 800 tpd (two parallel lines) | Design |
| Final overflow fineness | 80% passing 75 µm | Design |
| Grinding overflow concentration | 35%–38% solids | Design |
| Thickener underflow concentration (tailings) | >72% | Design/operating |
| Final concentrate moisture | 10%–12% | Design |
| ROM feed size | ≤350 mm | Design |
| Crushing product size | -15 mm | Design |
| Crushing circuit | Two-stage closed circuit | Design |
| XRT sorting commissioning | March 2023 | Trial production |
| Primary jaw crusher | PE600×900, 75 kW, 1 unit | Equipment table |
| Secondary cone crusher | PYH-3Z, 220 kW, 1 unit | Equipment table |
| Main screens | 2YKR2460H, 45 kW (1); ZKB2240 washing, 15 kW×2 (2) | Equipment table |
| XRT sorting machine | KK104-24-M, 22 kW, 1 unit | Equipment table |
| Grate ball mill | MQG2700×3000, 400 kW, 2 units | Equipment table |
| Fine ore bins | 718 m³ each, 2 units | Equipment table |
Technical qualifications
The report notes that the XRT intelligent sorting system, built in March 2023, is still in the process of adjustment and optimisation. The feed size class of the pre-sorting system is also under optimisation. The processing plant is designed for flexible operation: one or two grinding and flotation lines may run depending on mining supply quantity, with actual annual ore throughput ranging from 260 kt to 630 kt. No performance or economic data are provided in this recovery method section.
*Source: Technical Report on Gaocheng Silver-Lead-Zinc Project in Guangdong Province, China, effective 30 June 2024, Section 17 Recovery Method.*
NI 43-101 Technical Report Update on the Gaocheng Ag-Zn-Pb Project
This report updates the processing and recovery methods for the Gaocheng silver-zinc-lead project, describing the current flowsheet, operating parameters, and testwork basis.
Report context
The NI 43-101 Technical Report Update on the Gaocheng Ag-Zn-Pb Project in Guangdong Province, People's Republic of China, was prepared for Silvercorp Metals Inc. The report includes information on processing operations from trial operations starting in 2013, commercial production from 2015, and a process flowsheet optimization in 2019. The report presents design parameters, historical operating data, and metallurgical testwork results.
Processing route
Process overview
The overall process consists of crushing, grinding, sequential flotation of lead, zinc, and pyrite concentrates, and concentrate dewatering by disc filtration. An experimental tin recovery gravity separation circuit is installed on pyrite flotation tails.
The process flowsheet is very similar to the process adopted in the closed-circuit flotation tests described in Section 13.4.3 of the report. The tin recovery circuit is also shown in the flowsheet.
In 2019, the process was optimized by changing from zinc-sulphur priority flotation to zinc-sulphur mixed flotation followed by zinc-sulphur separation flotation. The quantity of ore processed has increased to around 300 ktpa.
Crushing
The crushing circuit consists of a run-of-mine ore bin from which ore is drawn by a vibratory feeder into the primary jaw crusher. The crusher product is screened on a vibrating screen, with -10 mm material conveyed to the fine ore bin and +10 mm material feeding a secondary cone crusher via a buffer storage bin. The fine ore bin has a capacity of 1,600 t.
Run of mine ore at -350 mm is reduced to crusher product at -10 mm.
Grinding
Two-stage grinding in ball mills achieves a product size of 80% passing 75 µm. The grinding circuit is sized for 1,600 tpd, with four mills with 400 kW motors installed. The circuit consists of a grate-discharge ball mill in closed circuit with screw classifier, followed by an overflow ball mill in closed circuit with hydrocyclones. The circuit is configured in two parallel trains, each of 800 tpd capacity.
The primary mills have weightometers fitted to feed conveyors linked to variable speed belt motors for mill feed control.
Flotation
The flotation circuit is configured in two parallel trains, following the grinding circuit configuration. Flotation cell sizing is adequate for 1,600 tpd, with rougher residence time designed to be a minimum of 15 minutes plus scavenger time of 15 minutes. Conditioning times of approximately five minutes apply.
The flotation process is a standard flotation of lead with three-stage cleaning, followed by zinc flotation with three-stage cleaning, leaving pyrite tailings as sulphur concentrate.
Concentrate handling
Concentrates are thickened and filtered on ceramic disk filters sized at 9 m², 15 m², and 30 m² for lead, zinc, and pyrite concentrates respectively. Filters are positioned above the concentrate storage shed for direct discharge. Concentrates are loaded by front-end loader into trucks for transport to smelter customers.
Tin recovery circuit
The experimental tin recovery circuit treats pyrite flotation tailings. After pre-concentration on eight sets of four-start spiral concentrators, the stream is cycloned to split at 75 µm. The +75 µm fraction is fed over 25 coarse shaking tables, and the -75 µm material is fed over 51 fine shaking tables. A final batch flotation stage removes residual sulphides.
Tin quantities produced to date are not material to overall mine economics.
Reagents
Reagent storage and mixing is located adjacent to the grinding and flotation plant. Reagents include:
- Depressants and modifiers: sodium sulphide, zinc sulphate, sodium sulphite, copper sulphate
- Collectors: di-ethyl dithiocarbamate, ammonium dibutyl dithiophosphate, butyl xanthate
- Frother: no. 2 oil (added directly)
Lime usage is large at 8 kg/t, with separate lime storage and milk-of-lime mixing area. Sulphuric acid tank and dosing pumps are separately located for safety reasons.
Process control and automation
Process control includes a central control room in the grinding-flotation building with TV imaging of key operating points, centralized monitoring of equipment run status, on/off interlocking of main crushing and grinding flows, and measurement and control of key parameters including ball mill feed tonnage, bin and tank levels, densities, flotation cell pulp levels, and reagent dosage. Automatic sampling covers key metallurgical accounting streams including flotation feed, concentrates, and tailings.
Ancillary facilities
The laboratory is equipped with sample preparation, wet chemistry, and basic photometric analytical equipment, as well as crushing, grinding, flotation, and gravity-separation metallurgical testing equipment. Routine analyses of ores and concentrates are conducted, along with water quality and environmental testing.
Maintenance workshops are equipped with craneage, welding, and basic machine-shop capabilities.
Key reported parameters
| Parameter | Unit | Value | Basis |
|---|---|---|---|
| Ore processed | ktpa | ~300–310 | Actual, from 2019 |
| Daily throughput | tpd | 900–950 | Actual |
| Design feed rate | tpd | 1,000 base / 1,600 expansion | Design |
| Grinding product size | µm | P80 75 | Design |
| Crusher product | mm | -10 | Design |
| ROM feed top size | mm | -350 | Design |
| Operating days | days/year | 330 | Design |
| Total installed power | kW | 5,043 | Design |
| Actual power drawn | kW | ~3,657 | Actual |
| Annual power consumption | kWh | 28,963,000 | Actual |
| Fresh water requirement | m³/t feed | ~0.4 | Design |
| Total water demand | L/day | ~3,200,000 | Design |
| Water demand at 1,600 tpd | L/day | 6,000,000 | Projected |
| Water recycle | % | ~90 | Actual |
| Lime consumption | kg/t | 8 | Actual |
| Feed head grade, Ag | g/t | 88–98 (LOM average 94) | Planned |
| Feed head grade, Pb | % | 1.26–1.69 (LOM average 1.48) | Planned |
| Feed head grade, Zn | % | 2.95–3.72 (LOM average 3.22) | Planned |
| Flotation rougher residence time | minutes | 15 min minimum | Design |
| Flotation scavenger time | minutes | 15 min | Design |
| Conditioning time | minutes | ~5 | Design |
Project website: https://silvercorpmetals.com/silvercorp-issues-updated-technical-report-for-the-gc-mine/
Technical qualifications
The report identifies several limitations and qualifications regarding processing information:
- There was no comminution testwork to serve as a basis for the crushing and grinding circuit design.
- Flotation testwork culminating in the closed-circuit test provided an adequate basis for flotation process design.
- Copper-lead separation was investigated but considered not viable by the qualified person, with limited Cu resource data available.
- A tin recovery circuit was considered to have potential merit but was not included in the base case for operations.
- The tin recovery circuit is described as experimental, and tin quantities produced to date are not material to overall mine economics.
- The qualified person considered necessary availability and utilization factors for 1,600 tpd throughput to be reasonable and in line with normal mining industry practice.
Source: NI 43-101 Technical Report Update on the Gaocheng Ag-Zn-Pb Project in Guangdong Province, People's Republic of China, Silvercorp Metals Inc., sections 17.1–17.8.
