The Selinsing Gold Mine is in a transition period as it moves from Oxide Gold Production to Sulphide Gold Production and in order to do that needs to convert the current oxide treatment plant to a plant with a sulphide treatment circuit. As a result the Selinsing operation is focused on preparation for Sulphide Gold Production. In the 2016 pre-feasibility study (“PFS”) a biological treatment approach was chosen as an economically viable option for the Company to maximize gold recovery from the sulphide material. (Snowden –Selinsing Gold Mine and Buffalo Reef Project NI 43-101 Technical Report-December 2016) The PFS revealed the Sulphide pre-treatment plant will require an estimated capital of $39.5 million, providing a $23.1 million NPV and 34.8% rate of return, and is expected to provide a six year life of mine. An additional biological pre-treatment circuit is planned to be added to the existing plant.
The Company is advancing the Feasibility Study for the Sulphide Project, which is based on the 2016 PFS and is focused on the delivery of a Front End Engineering Design (“FEED”) by applying BIOX® processing technology and an execution plan for construction of the existing plant upgrade including additional flotation and BIOX® processing circuits. The overall plant design package has been completed for review as well as the engineering design of the new processing facilities. Upon success of the Feasibility Study, FEED final design, and project financing, in-house construction and commissioning will follow.
The BIOX® Process is a patented technology for pre-treatment of sulphide-based refractory ores and concentrates ahead of a conventional cyanide leach for gold recovery. Positive BIOX® Process testwork results showed that over 90% sulphide oxidation occurred after 9 days, 98% after 15 days and 99% after the full 24 days. The sulphide oxidation levels show that representative samples of Selinsing/Buffalo Reef concentrates are amenable to the BIOX® process. Additional bioleaching variability testwork has shown excellent bioleaching kinetics with 98-99% sulphide sulphur oxidation achieved within 18 days. Cyanide leaching of the BIOX® residues achieved gold dissolution of 94-99% in the standard 24 hour tests. Additional flotation optimization testwork is being done to provide independent verification of the flotation conditions reported.
Mine planning and development work proceeded alongside the Feasibility Study including: evaluating the existing comminution circuit and laboratory flotation on site testwork, developing a 3D model of the proposed new flotation BIOX® plant and downstream processes. Scoping level design confirming the feasibility to expand the existing tailing storage facility has been done and slope stability studies for both the Selinsing and Buffalo Reef pits. The equipment specifications and data sheets have been used by the Company to get quotations from vendors. The quotations received have been combined with the material take-offs and schedules of rates to produce initial Capex and Opex estimates. Both Capex and Opex are under review and will be used for economic assessment in the Feasibility Study. Geological modelling and mine plan review and update are in progress to complete the internal Feasibility Study that will deliver the Sulphide Project Execution Plan, which is in progress.