Getting to know coal
As one of the natural mining resource, coal has heterogeneity and high complexity.
A number of experts have tried to give some definitions toward coal, which are:
1. Spackman (1958) : Coal is a solid carbon material composed with certain macerals.
2. The International Hand Book of Coal Petrography (1963) : Coals are sedimentary rocks that are combustible, formed from plants leftover in a variety level of preservations, tied by the process of compaction and buried within cavities on a variety level of depth, from shallow to deep.
3. Thiessen (1974) : Coal is a complex solid, formed from a variety of chemical elements or a complex organic solid.
4. Achmad Prijono, and friends (1992) : Coal is a solid hydrocarbon fuel that is formed from plants in a free oxygen environment and is affected by temperature and pressure for a long period of time.
From above resources, a definition can be concluded:
" Coal is a solid organic hydrocarbon fuel that is formed from plants that has went through putrefaction biochemically, chemically and physically in an oxygen free environment through a long period of time in a certain temperature and pressure."