FRONT End Engineering Design (FEED) work will lead to an internal definitive feasibility study (DFS) for Monument Mining’s Selinsing Sulphide Project in Malaysia. This process is based on follow-up test work on the 2016 pre-feasibility study (PFS).

The PFS recommends biological leaching to treat sulphide gold ores. A sulphide pre-treatment plant requires estimated capital of US$39.5 million and provides a US$23.1 million NPV and 34.8% rate of return, given approximately six years life of mine.

Additional test work was designed to determine which sulphide treatment technology among bio-leach, intensive acid leach and Intec hydrometallurgical process, can deliver best overall performance and economic recoveries for Selinsing and Buffalo Reef ore.

As a result, the BIOX® Process demonstrated best overall performance, showing on average 90% recovery of gold from Buffalo Reef representative ore samples. BIOX is a patented technology owned by Outotec and uses microorganisms in the oxidation of certain gold-bearing sulphides to facilitate gold recovery.

Monument expects the FEED work and DFS will be completed in September 2017. This will include the overall plant process design to set up FEED criteria, FEED for add-in flotation plant and BIOX Process plant, alterations to the existing processing plant, and internal DFS with an execution plan to move forward to a detailed engineering and construction stage.

The pilot plant built for Intec test work will be used for continuous test work on the BIOX Process over the life of sulphide production when ore characteristics change with mining at depth.

While Intec was not selected as the most suitable treatment on Selinsing/Buffalo Reef sulphide ore, ongoing test work with Intec will focus on production of very close to LME grade copper metal at the Mengapur project with the commercial objective of producing copper metal in-country at Mengapur.

Monument president and CEO Robert Baldock says the company is focusing on fast tracking the Selinsing Sulphide Project by producing an execution plan for construction.

During the March quarter, gold recovery decreased by 51% compared to the corresponding 2016 quarter to 2755 ounces and average head grade decreased 16% to 0.79 g/t. This was mainly due to the lower grade mill feed from stockpiled oxide and leachable sulphide ore.