Mineralogy

Dutwa is classified as a nickel laterite although it has unusual nickel laterite mineralogy compared with the better known equatorial nickel laterites of New Caledonia, Indonesia and the Philippines, and tropical Australian or South American nickel laterites which are currently either in production or development.

The geometallurgical properties of the Dutwa ore are unusually favourable for a lateritic ore and this sets Dutwa apart as an unusually strong nickel laterite project. The predominant ore types at Dutwa have been labelled Ferruginous Siliceous ("FeSi") and Transitional. The "FeSi" ore has a lower iron (10-15%) and higher silica (60-80%) content than its "Limonite" counterpart, which typically ranges from 25 to 40% iron and 15 to 30% silicon. The iron in both "Limonite", and "FeSi" ores must be dissolved to leach nickel. Limonite ores have a higher acid consumption when compared with Dutwa "FeSi" ore. Limonitic ores also frequently contain aluminium which also dissolves and makes solution purification more difficult. The Dutwa ores have low average aluminium content (< 1% typically). In addition the Dutwa ores have low levels of metals such as manganese, copper and zinc, which will improve the quality of the concentrate. These favourable "FeSi" and Transition ores collectively comprise greater than 95% of the Dutwa deposit.