The Pilar and Roça Grande deposits are examples of the Algoma BIF-hosted type. The main geological characteristics of this group are summarized as follows:

- Main host/fertile “Algoma-type” BIF Units: These units host the mineralization and are stratigraphically located at the waning stages of major volcanic cycles of the Rio da Velhas greenstone belt.

- Mineralization style: The mineralization consists of mainly “lateral” replacements/sulphidations of the iron carbonate-rich bands of the host Algoma-type BIF units. However, the BIF-hosted gold mineralization is not syngenetic in nature (in relation to the deposition of the host rock packages), rather it is clearly an epigenetic event that has occurred after the formation of the host rock units.

- Dimensions of the economic orebodies: Economic strike-lengths of only 50 m to 350 m for individual mined zones. Average thicknesses of the BIF-hosted orebodies may range from 2 m to 20 m.

The Pilar deposit is hosted by the basal units of the Nova Lima Group, and by sequences of the Quebra-Ossos Group. The rock packages in the immediate area of the mine are comprised of tholeiitic meta-basalts, mica-quartz schists, chlorite-quartz schists, quartzchlorite-sericite schists, and volcano-chemical and clastic meta-sedimentary rocks of the Santa Quitéria Unit (Nova Lima Group), and further to the east, of meta-komatiite flows (along with their intrusive equivalents) of the Quebra-Ossos Group. ........

There are two mining methods in use. The current LOMP forecasts longhole mining with delayed backfill for the majority of the Mineral Reserves. Mechanical cut and fill mining is used when ore geometry does not favour longhole mining.

Ventilation for the Pilar Mine is a pull system. Air is drawn down through the ramp and up an exhaust rise near the ramp. Ventilation on the levels uses auxiliary fans and vent ducting. Water is pumped to the surface using submersible pumps, pumped from level to level, then to the surface.

The Pilar Mine is accessed from a five metre by five metre primary decline located in the footwall of the deposit. The portal is located at an elevation of 760 MASL. The Pilar Mine is divided into levels with Level 01 established at elevation 690 MASL. All ore is hauled to the surface via the ramp using both contractors and company personnel. From this point, the level spacing is 75 m vertical, i.e., Level 02 is at elevation 615 MASL, Level 03 at elevation 540 MASL, etc. A three- metre-thick sill pillar is left between levels. Sublevels are excavated from the main ramp at 20 m vertical intervals to provide intermediate access to the mining panels. At each level and sublevel, drifts are developed near the centre of the mineralized zone to expose the footwall and to hang wall contacts. The drift is extended in both directions along strike, under geological control for alignment, continuing to expose the contacts until the limits of the depos ........

CRUSHING
The ore from the Pilar and Roça Grande mines is transported by trucks to the crushing circuit and placed in the ROM stockpile. The crushing circuit is made up of a CJ411 - 111 kW primary jaw crusher in open circuit, and secondary (CH440-223 kW) and tertiary (CH440 223 kW) cone crushers operating in closed circuit.

The ROM stockpile ore is fed to the jaw crusher with a front end loader though a grizzly and vibrating feeder. The jaw crusher discharge feeds a multi deck screen (3,500 mm x 1,800 mm – with three panel decks consisting of apertures of 75 mm, 35 mm, and 16 mm respectively top to bottom), the undersize of each deck feeds secondary crushing, tertiary crushing, or the final product conveyor respectively. The secondary cone crusher operates in closed circuit with a double deck screen (5,700 mm x 2,400 mm – with two panel decks consisting of 35 mm and 16 mm apertures). Product from the double deck screen either recirculates back to the secondary crusher, feeds the tertiary crusher, or goes to the final product conveyor. The tertiary cone crusher operates in closed circuit with a single deck screen (3,500 mm x 1,800 mm – with a panel deck aperture of 16 mm), with the oversize recycling to the crusher and undersize product going to the final product conveyor, which discharges onto the crushed ore stockpile. The final particle top size of the crushing process is 16 mm.

GRINDING
The grinding circuit consists of a 2240 kW ball mill (5 m x 6 m EGL) with a capacity of up to 100 tonnes per hour, operating in closed circuit with a series of hydrocyclones. The overflow from the hydrocyclones (-200 mesh or -74 µm) proceeds to the flotation circuit, and the underflow (+200 mesh or +74 µm) either feeds the gravity concentration circuit (75%) or is recycled to the ball mill feed (25%).

- subscription is required.