The coal seams of the Sydney coalfield are in several ways extraordinary, since no great differences occur either in rank or petrographic composition. Over a stratigraphic interval of 3,800 feet the volatile matter content varies between 36 and 40 percent (mineral matter free). All 12 seams, with the exception of one, may be classed as very bright coal containing between 73 and 84 percent vitrain, plus bright clarain. However, each seam contains dull coal horizons high in opaque matter and/or exinite. Concentration of these dull parts by washing, screening and crushing was the objective of this study. Coals were examined from the Emery and Harbour seams of the Sydney coalfield, and from No. 5 seam of the St. Rose field.The petrographic analyses were carried out with an integrating stage, using polished specimens of ground coal, mounted in lucite. Accuracy tests on this method were highly satisfactory.Results obtained are: 1. Washed coal is lower in opaque matter than non-washed coal, since opaque matter together with shaly impurities concentrates in the fractions of higher density. 2. Concentration of opaque matter by screening alone depends on the amount and distribution of this material in the seam. Fusain is always higher in the finest fraction. 3. A notable concentration of dull coal is obtained by pounding and subsequent screening. Grinding instead of pounding does not give results. Only by taking advantage of the natural differences in strength of the coal components can concentrations be obtained.

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