The Main Seam occurs in two 'pods', termed North and South, separated by
an east-west oriented 'want' zone (most probably a palaeo-channel). The seam on
either side of the 'want' area reaches thicknesses of over 30 metres but the
North Main Seam adjacent to the 'want' zone has been split into multiple seams
of 10 to 15 m thickness. Rock types in the inter-burden of this area are
characterised by inter-bedded sandstones and carbonaceous mudstones varying in
thickness from 0.5 to 5 m. In the South Main Seam, an area of un-split coal
exists and is characterised by few inorganic partings. Overburden in this area
varies geographically from relatively thick mudstones in the south and east part
of the coal deposit to inter-bedded sandstones and carbonaceous mudstones
adjacent to the 'want' area. The sandstone/mudstone overburden probably
represents a splay or splay-channel complex emanating from the larger 'want'
area palaeo-channel. Modelling lithological variability is of use because it is
one of the factors used in predicting cavability and roof support system design.
The coal in both the north and south deposits were found to exhibit highly
predictable quality and breakage parameters in relation to the coal geometry.
Although ash yield and sulphur are mostly low and not variable, volatile matter
and thus fixed carbon, varied in relation to seam thickness. In general,
volatile matter (dat) decreased and moisture increased with decreasing seam
thickness whereas moisture increased with decreasing seam thickness. In addition
to these parameters it was found that the energy needed to crush the coal was
lowest at the top and bottom of the seam and, on a whole seam basis, decreased
with seam thickness. All of these parameters were found to vary in relation to
the vitrain band content of the coal which itself was controlled by seam
geometry. These parameters can therefore be modelled and inputted into mining
plans and quality control operations.