Prior to Richards Bay Minerals' ownership of the project, some geological work had been completed by the privately owned Kangra Coal Group in the 1960's and 1970s. This was followed by further geological work, commissioned by Richards Bay Minerals (RBM) during the 1980's and 1990's before this project was sold to Riversdale in mid 2004.

The earlier studies had resulted in some 53 boreholes being drilled. In order to satisfy the requirement of an indicated coal resource complying with the JORC code, an additional 21 boreholes were drilled to meet these requirements.

Location
The Riverdale Anthracite Colliery (RAC) project area is centred on the Kwa-Ntabankulu mountain, located 30km south-east of Vryheid, following the Melmoth road.

It falls within the magisterial district of Vryheid, within the Kwa-Zulu Natal Province of South Africa (see location map).

Geology and Setting
The Vryheid Coalfield forms part of three major coalfields found in Kwa-Zulu Natal, and one of 19 coalfields found in the Karoo Sequence of South Africa.
The Vryheid Coalfield covers an area of approximately 2,500 km2 of which approximately 15% is underlain by coal seams (Bell and Spurr, 1996). The stratigraphy of the Vryheid coalfield is composed of the basal Dwyka Group (glaciogenic sediments) which is, in turn, succeeded by sediments of the Ecca and Beaufort Groups.

The seams within the Vryheid Coalfield are developed within a coal zone found in the Vryheid formation of the Ecca Group. The following seams occur within the Coal zone: Fritz seam, Alfred seam, Gus seam, Dundas seam, and Coking seam, all of which have been examined carefully through the various phases of exploration on site, it became apparent that the Fritz, Dundas and Coking seams were too narrow for commercial exploitation. The two seams left to be explored were the Alfred and Gus seams. For reasons of coal quality, Riversdale's investigations to date have focused solely on the Gus seam, which is characterized by anthracite of high rank, which is particularly low in impurities such as sulphur, phosphorous and calcium. Combined with other typical anthracite qualities, this places RAC in a position as the coal seams in the area are generally less than 1.5 metres thick. Transgressive dolerite dykes and sills are present which compartmentalize the mining areas into structurally controlled fault blocks. The dykes and sills affect the coal qualities in different ways: negatively where there is total devolatilization and positively where this is partial, resulting in the formation of anthracite.

Four Major Sills 
Four major dolerite sills have been identified in the RAC area. The most prominent sill is the Thabankulu sill which caps the Kwa-Ntabankulu mountain and can be seen outcropping on surface. Recent study indicates that this sill has no influence on the coal qualities. The other sills influence the coal qualities and there are areas of burnt coal. These sills can also cause displacements of up to 40 meters.

The Gus seam is well developed and the seam thickness ranges from 0.1 metre to 1.46 metres with an average thickness of 0.94 metres. The seam thickness exceeds 0.8 metres over most of the project area.

The Alfred seam lies 10 to 12 metres above the Gus seam. It is split by shale or siltstone parting into the Upper and Lower Alfred seams. The average thickness of the Upper seam is 0.52 metres, while the Lower seam averages 0.78 metres in thickness.

Due to the high variability in thickness only limited areas of the Alfred Seam will be economically viable and will require additional prospect drilling to take place from the Gus Seam horizon to prove the areas prior for potential exploitation. Due to the surface topography access to drilling sites on surface is very difficult and too costly and as such these reserves can not be evaluated at this stage. It is Riversdale's intention to exclude the Alfred seam from initial mine plans, and explore these seams from within mine workings for the Gus seam (see geological structure).

The total indicated resource area is 6 235 516 square metres. Of this 95 % is scheduled for mining and after taking geological and mining losses into account there is a total mined area of 3 041 206 square metres. The average seam width is 1.01 metres based on the minimum mining width of 0.8 metres, and using the raw relative density of 1.65 t/m, this converts to a probable reserve of 5 082 856 tons.

The Vryheid area has a long history of over 100 years of successful anthracite mining. Many of the mines closed in the 1990's due to the depletion of developed reserves and a slump in the anthracite price. There are still, however considerable small reserves of good quality anthracite in the area in a 50 kilometre radius around the town.

Mining
RAC plans to mine Gus and selected areas of the Alfred seams by means of bord and pillar and shortwall hybrid methods. Mechanised and semi-mechanised production sections will be responsible for mining coal while separate stonework teams will drill and blast the brushed areas including dykes and fault intersections. See Figure 4 for mine design layout.

The mine design is based on a slow build up to full production over a period of 18 months to 2 years. During the build up period some 9 000 to 11 000 tons per month will be produced. The total raw anthracite production planned per month, is 45,000 tonnes, which will only be achieved in year 3 (see mine design).

Two coal winning shifts are planned per day, with a third shift reserved for loading of rock blasted from brushing operations in the main travelling and belt road and in the course of negotiating the numerous faults and small dykes which are anticipated. A five-day working week is planned.