During the last few decades coal chemistry and coal petrology have developed as special fields of research, of equal importance from both the scientific and practical viewpoints. Until the nineteen twenties coal chemists used to examine coal as a whole. However, after coal petrographers had. discovered that practically all coals are composed of three groups of substances which differ widely in both physical proper• ties and chemical constitution, coal chemists, too, began to study each of the three petrographic constituents, the chemical constitution of which depends on rank. In this way coal science has been established on a broad basis.
The main field of coal petrology is coal microscopy. This branch has evolved much later than the microscopic study of inorganic rocks because of the difficulties which had to be overcome in the preparation of thin sections of coal. Nevertheless, the microscope was used for studies on British coals shortly after it had become available in an improved form.
Public attention was drawn to the practical value of coal microscopy for the first time by the 'Torbanite Case' in Great Britain (1854) which raised the question whether or not boghead coal should be regarded as coal.
Spores were first recognized in bituminous coal in about 1870, and coal micros• copy was used to prove that coal formed from the remains of terrestrial plants. In the same period the term 'coalification' was introduced to characterize the process of maturation of coal.
From 1892 to 1898 thin sections ob boghead and cannel coals were studied
microscopically, and the conclusion that boghead coal originated from algae was advanced in a series of publications.
From 1913 onwards, coal microscopy received particular stimulus from THIESSEN. In 1913, with WHITE, he published a comprehensive treatise called 'The Origin of Coal' extending to 390 pages and illustrated with photomicrographs. In 1920 he published his most important work under the title 'Structure in Paleozoic Bituminous Coals' with 160 plates showing numerous photomicrographs of thin sections of coal. It proved a real mine of knowledge and included much microscopic detail of bituminous coal. In 1956, the International Committee for Coal Petrology under• lined THIESSEN's outstanding role in the history of coal petrology by the creation of a THIESSEN Medal which is awarded to coal petrologists of special merit.
In 1919 STOPES described four rock types in bituminous coal making a distinction between vitrain, clarain, durain and fusain. In 1957 the system was enlarged by the introduction of two intermediate stages - duroclarain and clarodurain - which proved very useful in practice.

Tidak tersedia versi lain

Tidak Ada Data