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 9 ........

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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