Nuclear borehole logging is practically the only technique that has the capacity for providing quantitative in-situ coal quality information in real time. The SIROLOG gamma-gamma and neutron-gamma (PGNAA) borehole logging procedures have been providing vital characteristics of the coal seams at Callide coalfields since, 1993. Together with an accurate delineation of coal seams, the SIROLOG procedures estimate ash content, density and some ash constituents accurately enough for relatively inexpensive rotary chip holes to be accepted as points of observation in calculations of reserves. (C) 2003 Elsevier Science Ltd. All rights reserved.