MACERAL

microscopic organic component of coal consisting of an irregular mixture of different chemical compounds. Macerals are analogous to minerals in inorganic rocks, but they differ from minerals in that they have no fixed chemical composition and lack a definite crystalline structure. Macerals change progressively both chemically and physically as the rank of coal advances. (Rank constitutes position in the lignite-to-anthracite series and is primarily based on increasing carbon content and increasing fuel value.) Macerals are classified into three major groups: vitrinite, inertinite, and exinite. Vitrinite is derived from woody plant tissue and includes the macerals collinite and telinite. Most coals have a high percentage of vitrinites. The inertinite group comprises fusinite, micrinite, sclerotinite, and semi-fusinite, which are all rich in carbon. The exinite macerals, characterized by a high hydrogen content, include alginite, cutinite, resinite, and sporinite.