The Wolgan Seam of the Upper Permian IlIawarra Coal Measures of the Western Coalfield of New South Wales consists of high volatile, low sulphur, medium hard coking coal with high fluidity. This seam, 18-24m thick, in the Wolgan area, dips gently at 1_20 ENE and lies at 160-440m below the deeply dissected surface of the western margin of the Blue Mountains plateau.A detailed study of the deposit has revealed that the Wolgan Seam consists of four main coal plies separated by three distinct stone bands. Each of these subunits is lenticular and displays individual physical, chemical and mineralogical characteristics which exhibit distinct spatial distribution patterns across the area. Most noticeable is the presence of long linear ESE-trending zones of low ash - high volatiles - high fixed carbon - high fluidity which delineate the major distributary pattern within the deltaic environment of coal formation.This seam contains some of the highest fluidity coal in the world.The Wolgan area, close to the western margin of the Sydney Basin, is characterized by:I. a regional, closely spaced, homogenous joint fracture pattern dominated by an orthogonal pair set trending 3400 and 0700, to which the face- and butt-cleat directions respectively of the Wolgan Seam are sub-parallel, and2. a more widely spaced, heterogenous, cross-cutting pattern of regional structural fractures. Zones of bad roof conditions are probably associated with these lineaments which are subvertical and trend in three majordirections, viz., 005,035 and 115.