The manganese contained in the Plymouth deposit is predominantly in the form of a carbonate (rhodochrosite) whilst the iron exists in both oxide (hematite, magnetite and ilmenite) and carbonate minerals (predominantly siderite). The deposit type is sedimentary in origin and of the stratiform, BIF type. The host sequence consists of Silurian red and grey siliciclastic to calcareous siltstones and shales that have been metamorphosed under lower greenschist facies conditions. In addition to the main oxide, silicate and carbonate facies iron-manganese concentrations, host rocks contain minor magnetite and traces of pyrite in grey siltstone and black shale intervals. The manganese rich iron formation deposits occur in stratiform bodies and represent spatially distinct intervals that accumulated contemporaneously with surrounding sedimentary strata.

Iron and manganese are considered to have been deposited from seawater in an oxidizing environment and host strata have subsequently been structurally thickened through folding and faulting related to the Acadian Orogeny (middle to early Late Devonian in age). Some subsequent remobilization of manganese has occurred and resulted in re-deposition of manganese carbonate and oxides in fracture zones. Additional surficial weathering has also resulted in very limited oxidation at the overburden-bedrock interface, but is typically estimated to be limited to centimetres depth into bedrock.

Historical interpretation of th ........

The mining operation will use a conventional open pit mining method, off-highway haul trucks, and hydraulic excavator. The waste rock and mineral resource will be drilled and blasted using typical grade control methods and blasthole sampling.

Tetra Tech used an overall pit slope angle of 45°, as the required geotechnical data was not available to support the analysis required to assess the pit slope angles. Tetra Tech based this pit slope angle on estimates from previous projects and believes that this value is reasonable.

A conventional two-stage crushing plant is used to reduce the size of the ROM mill feed to the required size for grinding. After primary size reduction by the jaw crusher, the crushed material is conveyed to a screen where the oversize material is fed to a secondary cone crusher for final crushing. Final crushed material is stored in a fine ore storage silo.

The grinding circuit also utilizes a conventional two-stage, rod mill-ball mill configuration with the rod mill operating in open circuit and the ball mill operating in closed circuit. Size classification in the grinding circuit is by hydrocyclones. The target grind size of 80% passing 20 µm is based on achieving a similar particle size distribution in the feed to the pre-concentration circuit to that which was used in the preliminary magnetic separation test work.

The ground material will be fed as slurry through a dual-stage wet drum LIMS to remove ferromagnetic iron prior to entering the HGMS circuit. Bas ........