The Selinsing open-pit gold mine is owned and operated by Monument Mining, a mining company based in Canada. Located in Pahang State, Malaysia, the mine comprises both oxide and sulphide deposits.
The pre-feasibility study of the project was completed in 2016, while the feasibility study was completed in February 2019. The study focused on assessing the expansion of the existing oxide-based mine and extracting sulphide ore.
Sulphide ore mining at Selinsing commenced in the fourth quarter of 2019 and the ore processing started in the first quarter of 2020.
A gold sulphide flotation plant with a capacity of 950,000 tonnes per annum (tpa) was developed at the mine to process the sulphide ore. Construction of the floatation plant was completed in March 2023.
The transition from oxide to sulphide ore is expected to extend the mine life of Selinsing by six years. The expansion project is estimated to produce 223,000oz of gold over its six-year mine life.
Commercial production at the mine was achieved in September 2023.
Selinsing gold mine location
The Selinsing gold mine is located in Bukit Selinsing in Pahang State, approximately 158km north of Kuala Lumpur. The mine covers a total area of 150.3km2.
Selinsing gold mine history and development
In June 2007, Monument Mining acquired the gold mine, which comprises four properties, namely Selinsing, Buffalo Reef, Felda and Famehub. Oxide ore mining at the Selinsing and Buffalo Reef properties started in July 2009 and November 2012, respectively.
Ore is currently processed at the 40,000tpa processing plant, which began commercial operations in September 2010. The plant’s production capacity was increased to 1Mtpa in July 2012.
Selinsing gold mine geology and mineralisation
The Selinsing gold mine is located on a lineament known as the Raub Bentong Suture in Pahang.
The Selinsing property is hosted in an east-wards dipping shear zone, with the main mineralised shear hosting gold-bearing quartz veins and stockworks dipping to the southeast.
The mineralised shear zone is located within a sequence of felsic tuffs, clastic argillites and arenites, along with silicified sediments. High-grade mineralisation is contained in quartz complex veins and quartz-carbonate veins in the sedimentary rocks.
Gold mineralisation at the Selinsing property is contained within pyrite and arsenopyrite, while the mineralisation at the Buffalo Reef shear zone is structurally controlled and associated with Permian sediments.
The probable ore reserves at the Selinsing gold mine are estimated to be 5.734Mt grading 1.45g/t Au, while the contained gold is estimated to be 267,000oz.
Mining and ore processing
Conventional open-pit mining, involving drilling and blasting, is being applied at Selinsing. The extracted oxide ore undergoes three-stage crushing followed by ball milling, gravity recovery, cyanidation and carbon-in-leach (CIL) treatment to produce gold.
The existing 3,000tpd oxide ore processing plant was upgraded to treat sulphide ore. Stage one of the sulphide flotation plant includes a concentrate thickener, a water recovery thickener, reagent storage and mixing and concentrate filtration.
The flotation circuit comprises a trash screen, two conditioning tanks and six rougher tank cells. The sulphide ore undergoes three stages of a cleaner flotation process, which includes the addition of various reagents such as soda and sodium sulphide.
The final flotation concentrate is transferred to a concentrate thickener. The thickened slurry is transferred to a concentrate filtration plant, followed by a concentrate storage tank and pumped to a concentrate filter press.
The concentrate filter reduces the moisture content in the thickened slurry by 85% to 90% to produce a gold concentrate cake, which is transported in containers or bulk bags and shipped to customers.
Stage two of the sulphide flotation plant will include the development of a new BIOX® CIL circuit, which will process the refractory sulphide ore and concentrates that cannot be recovered by conventional cyanide leaching.
The Selinsing mine can be accessed through sealed roads from the regional centres of Kuala Lipis and Raub.
Power supply for the mine is provided by Tenaga Nasional Berhad from Kuala Lipis via a new 33 kV line.
The nearby Sungai Kermoi River is the main water supply during sulphide ore extraction and processing.
A new 1.5MW diesel-fuelled generator was used temporarily to power the project office, site accommodation, main administration building and construction equipment.
Workers were accommodated at a new site accommodation camp near the valley adjacent to the main office during processing plant construction.
Minetech Construction, a construction company, was engaged as the mining contractor for the Selinsing gold mine.
Snowden, a consulting company, prepared the pre-feasibility study of the project, while Practical Mining, a geologic and engineering services provider, conducted a study for the extraction of sulphides.
SRK Consulting, a mining consultancy, conducted the scoping study of the expanded tailings storage facility, while Peter O’Bryan and Associates prepared the slope stability analysis for the Selinsing and Buffalo Reef deposits.
Outotec (now Metso Outotec) designed the BIOX facility for Selinsing, while Orway Mineral Consultants was engaged for the overall plant design.
Contromation Energy Services, an engineering and construction services provider, drafted the engineering structure for the new processing units at the Selinsing gold mine.
Mincore, a consulting company, conducted the detailed engineering design for the floatation plant.
The main contractor for the project was the construction company Seong Henng Engineering Works.
BGRIMM Machinery and Automation Technology, a mining equipment supplier based in China, supplied the flotation cells for the flotation plant.
Metso Outotec Australia, a mining and construction equipment provider, supplied the thickeners, while McLanahan, a process solutions provider, supplied the filter press.