For at least 70 years most coal geologists and coal petrologists have agreed that there is some sort of a general progression from peat through various coals all the way to anthracite. The terms which have been applied classically to this sequence are peat - lignite - subbituminous - bituminous - semi-bituminous - semi-anthracite - anthracite - and meta- anthracite. At one time some authors felt that specific vegetational types gave rise to different rank coals. Most people do not hold with this interpretation at the present time. Throughout the sequence noted above, many changes take place and it is the measurement of these changes, or the parameters which are used to measure these changes, which give rise to the word rank.
The International Committee for Coal Petrology in the second edition of the International Handbook for Coal Petrology (1963) agreed that the term rank should be accepted as an international scientific term. They suggest "degree of coalification" as a synonym for rank. As a definition for the word they suggest, "describes the stage of carbonification attained by a given coal". The tricky part, of course, now becomes how do we measure the degree of carbonification or coalification.
Figures & Tables
It is the intent of this course to deal with the very broad aspects of coal petrology. In the process of doing this, the authors intend to point out many of the areas in which the science has been applied to geological and various production problems and also to suggest some areas where future work may be of value. The emphasis is to provide some basic reference materials, some procedural techniques and possibly some ideas for those of you who wish to pursue work in this area. This course is not intended to train you as a coal petrologist but rather to give you some ideas of what the capabilities and limitations of the field are, and to help you get started on your own if you wish to pursue any of these ideas to greater length.