Inertinite macerals

The third maceral group, inertinite, originates from plant remains similar to vitrinite but oxygen has usually played a stronger role during the biochemical stage of coalification and has been incorporated into the macerals either before or during their incorporation into peat. 

Some of the cell structure of the wood may appear to be well preserved and, as is to be expected, transitions can exist between inertinite and vitrinite. Typically, the plant material in the inertinite macerals has been strongly altered and degraded in the peat stage of coal formation. For example, fossil charcoal is the inertinite maceral, fusinite. 

In most North American coals, the inertinite macerals range from less than 5% to as much as 40% with the highest amounts generally occurring in Appalachian coals. However, the inertinite macerals can make up over 50%-70% of some western Canadian coals. 

On the other hand, semifusinite is intermediate between fusinite and vitrinite showing the well-defined structure of wood, but the cell cavities (round, oval, or elongated) vary in size and are smaller and sometimes less well-defined than those of fusinite. Semifusinite has the cell texture and general features of fusinite except that it is of lower reflectance. In fact, semifusinite has the largest range of reflectance of any of the various coal macerals going from the upper end of the pseudovi-trinite range to fusinite. Semifusinite is also the most abundant of the inertinite macerals. 

On the other hand, micrinite is composed of smaller material and is believed to be a maturation product of protoplasm. Micrinite occurs as very fine granular particles of high reflectance and is commonly associated with the liptinite macerals but sometimes gives the appearance of actually replacing the liptinite. Micrinite is frequently, but not always, found in association with microspores. It is also found in the sapropelic (cannel and boghead) coals. Both macerals are virtually structureless. 

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There are certainly lithotypes that can be handpicked from European and American coals that are relatively rich in fusinite and semifusinite. However, it is perhaps significant that the mean content of total fusinite + semifusinite in 697 coal samples in the Penn State/DOE Data Base is 8.9%. On the other hand, the content of inertinite macerals in the Permian coals of Gondwana-land is notoriously high and much of this inertinite material consists of semifusinite (5,26,33,34), the concentration of which can be as high as 50% in the whole seam. 

Earlier publications have documented the higher reactivities of vitrinite and liptinite group macerals and the lower reactivities of certain inertinite macerals in liquefaction (50,57,68). 

Inertodetrinite maceral occurring as individual, angular, clastic fragments of other inertinite macerals, surrounded by other macerals, commonly vitrinite or minerals, and also distinguished by a reflectance higher than that of associated vitrinite. 

D. Inertinite macerals, seini-fusinite at left and fusinite at right. 

Part of this data in Table II is a series of British maceral concentrates. The Woolley Wheatly Lime sample is 93% fusinite while the Teversal Dunsil concentrate is 80% semifusinite with 13% fusinite. The Aldwarke Silkstone sample contains 43% semifu-sinite and 43% fusinite. The petrographic analysis of PSOC-2 reveals nearly equivalent amounts of fusinite, semifusinite, micrinite, and macrinite (6.8, 8.1, 7.5 and 8.5% respectively in the whole coal) while PSOC-858 contains primarily semifusinite as the inertinite. The differences in faH values for these iner-tinite samples are greater than the experimental error and these differences suggest that NMR techniques may be useful in characterizing the chemical structural differences between inertinite macerals. 

There have been a large number of electron spin resonance (ESR) studies of coal and coal products,(1J but a microscopic interpretation of the resulting data has been hampered by the chemical heterogeneity of the coal samples examined. While several surveys of specially selected macerals have appeared, 3), the recent evolution of maceral separation techniques - now allows detailed ESR observations to be made on coals systematically fractionated in which coal rank, maceral type, and maceral density are simultaneously distinguished. The present report surveys the behavior of a variety of ESR properties of carbon radicals in exinite, vitrinite, and inertinite macerals in a variety of coals of different rank. These data... 

Among the inertinite macerals are opaque modifications of vitrinite, termed fusinite and semifusinite,... 

Of the three maceral groups, vitrinite is more familiar as the brilliant black bands of coal. Vitrinite macerals are derived from the cell wall material (woody tissue) of plants, which are chemically composed of the polymers, cellulose and lignin. The vitrinite group is the most abundant group and typically makes up 50%-90% of most North American coals. However, most Gondwanaland coals and some western Canadian coals are vitrinite poor —the inertinite macerals dominate in these coals. 

Liptinites generally make up about 5%-15% of most North American coals. They are usually more abundant in the Appalachian coals than any other US coals except cannel and boghead types where they dominate. At a reflectance of 1.35-1.40, most of the liptinite macerals disappear from coal. Cannel and boghead coals are petrographically distinguished from humic coals by both their maceral composition and texture. They have an abundance of liptinite macerals (sporinite in can-nels and alginite in boghead coal) and a relative low level of vitrinite and inertinite macerals. 

Two predominantly inertinite macerals are fusinite and semifusinite (Figure 4.3) fusinite is commonly referred to as fossil charcoal and usually shows well-defined cellular structures. Fusinite is seen in most coals and has a charcoal-like structure. Fusinite is always the highest reflecting maceral present and is distinguished by cell texture. It is commonly broken into small shards and fragments. 

Fusain is fossil charcoal, a coal lithotype sometimes called mother-of-coal . Fusain is dominated by the inertinite maceral group (see coal) and composed of carbon rich, partially oxidised plant remains. The material has no fuel value but produces a velvety black pigment, similar to charcoal. However, this can also refer to a charcoal crayon made of the wood of the spindle tree (Euonymus europaeus L.), called in French fusain, and drawings made thereof (OED, 2002, citing nineteenth century examples). 

The characteristic optical property of inertinite macerals is their comparatively high reflectance as it can be seen in Figure 3.1a-e. Although the precursors of inertinites are the same as for vitrinites, namely cellulose and lignin from plant... 

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