System of symbols for coal and transitional rocks to facilitate graphic documentation of a coal seam


Authors: Honěk J, Hoňková K, Staněk F

Published in: Bulletin of Geosciences, volume 74, issue 2; pages: 233 - 242;

Keywords: Coal deposits, database, petrographical classification, technological classification, petrographic designations,

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Two classifications for coal and transitional rocks were elaborated - technological classification with variable limits of evaluation of coal as mineral raw material and petrographical classification with invariable limits of classification for evaluation of coal as a sediment. The basic petrographic division of coal and transitional rocks is based on the relative proportions of organic and inorganic components of the coal substance, as expressed by the content of ash Ad. Five groups of coal can be distinguished based upon this parameter. Coals and ash coals are further subdivided according to the proportions of the major petrographic components (according to the occurrence of detritic and xylitic components in brown coals or according to dull or bright components of bituminous coals). Symbols for ash coal and all transitional rocks represent a combination of coal and sediment symbols. Various genetic types and transitional rocks were also given specific graphic symbols. Special symbols were developed for sections of coal seams examined only by well logging, for deformed seam, for coals and transitional rocks broken by drilling, etc.