Company Limited was then created to undertake a detailed economic evaluation of the prospect, with more intensive work beginning in the late 1980s. Société Aurifere de Guinea (SAG) took over from its predecessors and continued work on the placer deposits. Production on the Koron placer reached a peak in 1992 with 1.1t gold being produced, although due to a number of difficulties, the mine was shut down later that year.
In the mid-1990s, Golden Shamrock acquired and operated the project as an open pit and heap leach. In October 1996, Golden Shamrock was acquired by Ashanti Goldfields Corporation which operated Siguiri as a heap leach until 2004. Ashanti Goldfields Corporation merged with AngloGold Limited in 2004 to become AngloGold Ashanti. AngloGold Ashanti completed the design and construction of the 8.5Mtpa saprolite soft rock treatment plant and commissioned it in 2005. This was later increased to 12Mtpa.
A Siguiri combination plant feasibility study, based on the requirement to process fresh and transitional material in combination with existing oxide material, was completed in 2015. The combination plant conversion project began in 2017 to allow the mine to treat 6Mt of hard fresh rock ore and 6Mt of oxide ore. Construction was completed in March 2018 and further optimisation and debottlenecking of the plant continues.