The U.S. Geological Survey coal quality (COALQUAL) database version 3.0

Data Series 975
By: , and 



Since the mid-1970s, the U.S. Geological Survey (USGS) has maintained a coal quality database of national scope named USCHEM, which currently contains data for over 13,000 samples. A subset of the USCHEM database called COALQUAL Version 1.3 was initially published in 1994 and was followed by Version 2.0 in 1997. Version 3.0 of the COALQUAL database represents a major editing effort to resolve some of the DOS software limitations used by earlier versions of the database.

Because of database size limits during the development of COALQUAL Version 1.3, many analyses of individual bench samples were merged into whole coal bed averages. The methodology for making these composite intervals was not consistent. Size limits also restricted the amount of georeferencing information and forced removal of qualifier notations such as "less than detection limit" (<) information, which can cause problems when using the data. A review of the original data sheets revealed that COALQUAL Version 2.0 was missing information that was needed for a complete understanding of a coal section. Another important database issue to resolve was the USGS "remnant moisture" problem. Prior to 1998, tests for remnant moisture (as-determined moisture in the sample at the time of analysis) were not performed on any USGS major, minor, or trace element coal analyses. Without the remnant moisture, it is impossible to convert the analyses to a usable basis (as-received, dry, etc.). Based on remnant moisture analyses of hundreds of samples of different ranks (and known residual moisture) reported after 1998, it was possible to develop a method to provide reasonable estimates of remnant moisture for older data to make it more useful in COALQUAL Version 3.0. In addition, COALQUAL Version 3.0 is improved by (1) adding qualifiers, including statistical programming to deal with the qualifiers; (2) clarifying the sample compositing problems; and (3) adding associated samples. Version 3.0 of COALQUAL also represents the first attempt to incorporate data verification by mathematically crosschecking certain analytical parameters. Finally, a new database system was designed and implemented to replace the outdated DOS program used in earlier versions of the database.

Suggested Citation

Palmer, C.A., Oman, C.L., Park, A.J., and Luppens, J.A., 2015, The U.S. Geological Survey coal quality (COALQUAL) database version 3.0: U.S. Geological Survey Data Series 975, 43 p. with appendixes,

ISSN: 2327-638X (online)

Table of Contents

  • Abstract
  • Introduction
  • Purpose of COALQUAL Version 3.0 Database Revision
  • Editing Results
  • Error Estimation
  • Data Validation
  • Conclusion
  • References Cited
  • Appendix 1. Acceptance Rules for Upper Level Data
  • Appendix 2. Data Parameters
  • Appendix 3. Data Qualifiers
  • Appendix 4. Remnant Moisture Estimate Method 
  • Appendix 5. Averaging Components Used to Calculate Upper Level Samples
  • Appendix 6. Strat Parameter
  • Appendix 7. Identification of Nearby Samples 
Publication type Report
Publication Subtype USGS Numbered Series
Title The U.S. Geological Survey coal quality (COALQUAL) database version 3.0
Series title Data Series
Series number 975
DOI 10.3133/ds975
Year Published 2015
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Eastern Energy Resources Science Center
Description Report: v, 50 p.; Database
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details