The coals of the upper part of the Mansfield, Brazil, and the lower part of the Staunton Formations (Atokan and Desmoinesian, Pennsylvanian) in Indiana (Illinois Basin) are characteristically thin and discontinuous. As a result, problems with correlation and identification of the seams have persisted for both researchers and industry. These discrepancies affect coal exploration, mine planning, and subsequently coal-fired utilities. This study presents exploration and operational examples demonstrating some of the correlation problems associated with the coals of the Brazil Formation, and the Upper Block and Lower Block, in particular, and the surrounding upper part of the Mansfield Formation and lower part of the Staunton Formations. Based on exploration boreholes, mine scale observations, and coal quality and petrographic data, this study suggests that (1) the coal mapped as the Upper Block Coal Member of Clay County may, in fact, be the same seam as the Lower Block Coal Member of Daviess County; and (2) the Lower Block coal of Clay County is not present south of the Switz City area of central Greene County, IN. ?? 2003 Elsevier Science B.V. All rights reserved.