Geology Reference
In-Depth Information
On a microscopic scale, three macerals, the organic equivalent of minerals (Stopes, 1935), were identified:
vitrinite, exinite, and inertinite. Vitrinite, typically shiny and glassy, is the coalified remains of cell walls, woody
tissue of stems, branches, leaves and roots of plants, and the precipitated gels from these materials. In white light,
vitrinite is a pale-gray to white. It is the predominant maceral in coal, and is the only important component of
vitrain. It has a relatively high concentration of oxygen and a moderate amount of hydrogen and volatile matter.
Exinite was formed from waxy resinous debris, and is divided into sporinite, alginite, resinite, and cutinite. It is rich
in hydrogen and is primarily aliphatic. Inertinite, the third maceral, is formed from oxidized wood or bark. It is
aromatic and has low-volatile matter content. The relatively unreactive inertinite which forms fusain is made up of
macrinite and micrinite, massive or granular residues of protoplasm. Also, fusinite is oxidized woody tissue in
which the cell structure is still visible, semifusinite is less oxidized, and sclerotinite is formed from fungal remains
(Petrakis and Grandy, 1980).
The preceding information on coal, how it is formed and its composition, is intended as a general overview. For
more detailed information, consult the listed references.
