The Otjihase deposit comprises five sub parallel, spatula-shaped, mineralised zones namely Shoot A, Shoot B, Shoot 2, Shoot 3 and Shoot 4. Shoots A and B are known collectively as the Main Shoot in mine terminology because of their close proximity, but geologically they are separate entities. The shoots consist of massive sulphides composed primarily of chalcopyrite and pyrite, hosted in a magnetite rich quartzite. Of the five, only Shoot A is consistently mineralised and forms the bulk of the mineral resources.

With the exception of Shoot B, which is slightly elevated above the southern margin of Shoot A, the westerly-plunging mineralised shoots occur at approximately the same stratigraphic level and are separated by more than 150m of barren or weakly mineralised quartz-mica schists that dip north westerly at 16°.

The northern margins of the shoots are abrupt, whereas the southern margins are gradational, consisting of thin bands and lenses of mineralisation, or disseminated mineralisation, in the quartz-mica schist country rocks. The footwall contact between the lowermost mineralised band and the underlying quartz-mica schists is usually sharp. The hangingwall contact is often gradational due to the presence of zones of disseminated mineralisation.

Each of the shoots has a gossanous outcrop and extends down plunge for more than eight kilometres. The mineralised shoots are cut by a series of sub-vertical northerly trending normal faults that ........

Historically, mining has been by means of room and pillar with primary extraction rates ranging from around 80% to 85% in the upper Otjihase compartment to 45% in the Kuruma compartment.

The Otjihase compartment extends from the surface down to a depth of approximately 260m below surface. The upper area, down to around 180m below surface was mined by JCI using a room and pillar system based on 5m by 5m square pillars with 15m wide rooms on dip and strike.

The ore is trucked to an underground crusher station immediately east of the Hoffnung East fault from where it is transported by means of 10 conveyor belt sections to a point where it is tipped into kibbles pulled by locomotives which take the ore the last 1.5km to the mill receiving bins on surface.

Ore from the Otjihase mine will be crushed underground through a jaw crusher to a nominal 150mm prior to being transported to surface, to a 3,200t receiving bin at the plant. Ore from Matchless mine is road hauled and similarly crushed at Otjihase ahead of the same receiving bin. The receiving bin has 14 off take points feeding a single conveyor.

The different ore types are stored separately in the receiving bin with no mention or plan of blending practice. The ore ratio is expected to be 35,000t:15,000t Otjihase: Matchless, and some consideration may be given to blending is based on the flotation response and the quantity of ores available.

The crusher plant consists of a primary grizzly with oversize being crushed in the 5½ft Standard Symons secondary crusher. The grizzly fines are screened on a vibrating screen to reduce the load on the tertiary crusher. The screen oversize and the secondary crusher product are conveyed to a surge bin then to the tertiary screen and tertiary crusher, a 5½ft Shorthead Symons. The screen undersize is directed to three fine ore silos whilst the screen oversize is crushed in the tertiary crusher and recycled back to the screens where the fines are removed. This is a very conventional crusher circuit. The final crusher product size will nominally be 100% passing 10mm.

Crushed product is conveyed to three mill feed silos each with 1,100t capacity. Crusher plant spares observed include mantles, bowls and screen parts. The condition of this circuit is considered to be reasonable but some maintenance and checking is necessary before commissioning. The dust extraction system at the crusher plant should be checked prior to the planned start-up, particularly all ducting.

Milling plant
The milling circuit consists of three closed circuits Vecor 10ft x 12ft ball mills with 20” hydrocyclones. Mill motors are 670Kw with 11Kv supply. Historically the grind was approximately 80% passing 250 micron. The milling circuit configuration is very conventional, and considered suitable for the type of ore to be processed. The three old Ramsey weightometers measuring mill feed tonnages will be replaced with new process control units which may be configured to give some degree of automation and control.

The ball mills operate with rubber liners and lifters with 56mm plus 64mm cylpebs as grinding media. While the mills have not been run over the past year, barring gear units have been used to turn the mills to ensure that bearings and lubrication are functional. As with other parts of the plant, all equipment should be checked, cleaned and motors turned before startup.

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