Zinc-Pb orebodies in the Dairi deposit are distributed along a 4-km SE-NW strike in the eastern flank of the Sopokomil Dome. From top downward, the rocks in the Sopokomil Dome consists of interbedded calcareous siltstones-sandstones (Dagang unit), interbedded carbonaceous shales-calcareous siltstones (Julu unit) and massive as well as brecciated dolostones (Jehe unit).

The Anjing Hitam prospect is situated in the southeastern portion of the Dairi deposit. At the Anjing Hitam prospect, orebodies are hosted in the Julu unit and display stratiform and concordant morphologies.

Two mineralized horizons are present, namely the upper and main mineralized horizons. The upper mineralized horizon occurs as lenses and it is sporadically distributed throughout the prospect while the main mineralized horizon is continuous. The orebodies attain maximum thickness of 30 m in the main mineralized horizon.

The Dagang and Julu units are composed of quartz, carbonate minerals, muscovite and organic matter. Quartz and carbonate minerals are dominant in the sandstones and siltstones layers of the Dagang and Julu units while muscovite and organic matter are dominant in the shales layers of the Julu unit. Zircon and sphalerite occur in trace amounts in the Dagang and Julu units.

According to ore minerals abundance and their textural relationship, the Anjing Hitam prospect hosts five ore types: (1) pyrite-rich massive ore, (2) sphalerite-rich massive ore, (3) bedded sulfide ore, (4) galena-rich breccia ore and (5) vein ore.

Pyrite-rich massive ore is composed of abundant pyrite with sphalerite-galena intergrowth in the interstices.

Sphalerite-rich massive ore is characterized by sphalerite-galena intergrowth with trace to minor amounts of pyrite.

Bedded sulfide ore is identified as interbedded host rocks and sulfide-rich layers with individual layer up to 1 cm thick.

The sulfide-rich layers are subdivided into pyrite-sphalerite-rich and galena-sphalerite-rich subtypes.

Galena-rich breccia ore consists of host rock fragments cemented by galena with trace amounts of tetrahedrite, bournonite and pyrrhotite. Coarse-grained pyrite up to 3 mm in size also occurs in this ore type.

Vein ore is associated with open-fracture filling in the host rocks and other ore types. This ore type is dominated by the sphalerite-galena intergrowth.

There will be three portals: haulage, service and ventilation. The portals will be accessed via a surface haul road and mined conventionally (drill and blast). Mining methods will be mainly long hole open stoping, primary-secondary longitudinal bench stoping and cut & fill.

Mining voids will be filled with paste fill which will prevent subsidence, maximize resource recovery and limit the size of the tailings storage facility (TSF). Ore and waste will be trucked to the surface via the haulage decline to a run of mine (ROM) ore transit storage area.

Waste rock will be used for the backfill of avoids in the mine and for the construction of the TSF. Ground support will be a combination of bolts and mesh, shotcrete/fibrecrete, cable bolting, rock fill and paste fill.

The ventilation circuit will consist of two (2) fresh air intakes via haulage and service portals and a series of rises to bring fresh air to the production areas. Exhaust is via a parallel system of ventilation rises and drives connected to the ventilation portal.

Water management will consist of development sumps, transfer sumps and pumps, including a main pumping station and a surface settlement pond.

From the ROM, Ore will be sent to processing plant for crushing and processing.

The plant and equipment for a one million tonnes per annum (Mtpa) ore processing plant equipment is in storage and care in Medan awaiting fabrication at the mine site. The plant is designed to produce high grade zinc and lead sulfide concentrates at the rate of up to 225,000 tonnes of zinc sulfide and 105,000 tonnes of lead sulfide per annum.

After trucking from the underground workings to a run of mine (ROM) storage area, ore will enter the plant for processing.

The processing stage will commence with the ore undergoing single stage jaw crushing, semi-autogenous grinding (SAG) and ball milling, flotation, thickening, filtration and drying.

Much of the bulk tailings from the processing plant will be sent to a paste plant for blending with cement to form a paste which will be injected back underground as backfill for empty mine workings. The remaining tailings wil ........