The Twangiza property can be divided into three distinct litho-structural terrains which can be seen in the figure below. The eastern terrain is characterised by N-S trending Neoproterozoic sediments, which are part of the Itombwe synclinorium, a regional-scale fold which extends southwards from the Twangiza area for about 150 km.

The sediments in the Neoproterozoic terrain are generally very weakly metamorphosed. The dominant lithology is mudstone, often with a significant amount of carbonaceous material. Subordinate units of siltstone are commonly interbedded with the mudstone, being slightly coarser, more siliceous and harder. Quartz wacke and sandstone occur locally, but are usually confined to relatively thin beds or lenses which lack continuity.

In the vicinity of the Twangiza Main and North deposits, the Neoproterozoic sediments have been intruded by porphyritic sills, ranging in thickness from less than 1 m to over 50 m. The sills have undergone extensive hydrothermal alteration and the original composition is difficult to determine. However, it is possible that the sills are part of a suite of alkaline intrusive rocks that were emplaced along the line of the present-day Western Rift, at about 750 Ma. Small granitic intrusions have been found in the Neoproterozoic rocks, and have been locally exploited for tin by colonial prospectors and artisanal miners. It is believed these granites are younger than the G4 tin granites which were emplaced at 975 Ma, and may also be related to the same 750 Ma intrusive event as the porphyry sills.

The Twangiza Main ore body consists of a wide (up to 200 m) zone of pervasively altered mudstone, siltstone and porphyry sills, with abundant sulphidic veins. The veins form a complex irregular network, although veining parallel to bedding is relatively common. Hydrothermal fluids have exploited both the fracture system which developed during folding due to competency contrasts between the lithologies, and dilational zones between bedding planes to form saddle reefs.

The style of mineralisation in the sediments and sills varies, but can be sub-divided into two main types as discussed below:
Mineralisation in the sills is characterised by the presence of pyrite and arsenopyrite (approximately 65% pyrite: 35% arsenopyrite). The total abundance of sulphide is variable, averaging about 3% of the rock, but locally comprising up to about 30% of a 1 m sample. There is a positive correlation between grade and sulphide content. The sulphides occur in a variety of habits: (a) disseminated crystals, (b) stringers, (c) coarsely crystalline veins up to 10 cm in width, but usually 1 – 3 cm across, and often with intergrown quartz, and (d) irregular massive patches.

Mining operations are based on conventional open cast techniques. Excavation of the ore and waste rock on 2.5m high mining benches will be performed by hydraulic excavators in backhoe configuration loading out to 40 tonne nominal capacity articulated dump trucks (Bell B40D or Cat equiv.). Mining is free dig in the oxide zone with any harder transition and fresh materials drilled and blasted on 5.0 m benches.

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The processing plant comprises portions of two second-hand plants which were purchased in Australia, respectively a crushing, screening and grinding section and a leach, adsorption and elution section. The proposed Twangiza Process Plant design is based on a well known and established Gravity/Leach & CIP technology, which consisted of three-stage crushing, ball milling, gravity recovery of free gold followed by leaching/adsorption of gravity tailings, elution & gold smelting and tailings disposal. However during further testing CIP tanks were changed to CIL which result in better recovery of the ore.

Gravity and Intensive Cyanidation
A portion of the cyclone underflow can be diverted from splitter box No.1 over the 1.12 mW x 2.40 mL gravity feed screen to remove the +2mm material. Dilution water is added onto the screen to dilute the feed slurry to a solids density of 45% by weight. The screen oversize is recycled back to the no.1 ball mill. The screen undersize is fed ........