The Petrology of Resinite in American Coals - ACS Symposium Series

Chapter 12

The Petrology of Resinite in American Coals John C. Crelling

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Department of Geology, Southern Illinois University, Carbondale, IL 62901

Resinite macerals are ubiquitous, though minor, components in most American coals below medium-volatile bituminous rank. They are usually absent in coals of higher rank. Although resinite macerals usually make up less than 3% of most U.S. coals, they are particularly abundant in coal of the Wasatch Plateau in Utah where they can account for as much as 15% of the macerals present. Resinite macerals have two common modes of occurrence. In most Appalachian and midwestern U. S. coal seams resinites occur as primary (present at the time of deposition) ovoid bodies with a long axis rangingfrom25 to 200 micrometers. While primary ovoid bodies of resinite are also found in western U.S. coals of Cretaceous/Tertiary age, much resinite in these coals occurs as secondary cleat and void fillings. This secondary resinite shows an intrusive relationship to the host coal and often shows flow texture and carries xenoliths of coal in resinite veinlets. Fluorescence microscopy reveals that only the primary resinite ovoids commonly show "oxidation" or "reaction rims" that suggest a surface alteration. Fluorescence spectral analysis can usually distinguish resinite from other macerals and in most cases it can also distinguish between different resinites.

Resinite macérais are ubiquitous, though minor, components in most American coals below medium-volatile bituminous rank. They are derived from resins in the original plants that were the precursors of the coal. Resinite macérais have two common modes of occurrence. In most Appalachian and midwestern U.S. coal seams resinites occur as primary (present at the time of deposition) ovoid bodies with a long axis ranging from 25 to 300 micrometers. While primary ovoid bodies of resinite are also found in western U.S. coals of Cretaceous/Tertiary age, much resinite in these coals occurs as secondary cleat and void fillings. Although resinite macérais occur in almost all U.S. coals, they are particularly abundant in some western U.S. coals and much of the published pétrographie literature deals with resinites from this area (1-10). It is also observed that the resinite in the

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Anderson and Crelling; Amber, Resinite, and Fossil Resins ACS Symposium Series; American Chemical Society: Washington, DC, 1995.


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The Petrology of Resinite in American Coals

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western U. S. coals of Cretaceous and Tertiary age tends to commonly occur in cleats and fissures where it is observable megascopically. Similar cleat andfissure-fillingresinite in coals from England has been reported (11-13). The authors concluded that the increased temperature and pressure of coalification in the bituminous range was sufficient to gently mobilize some of the resinite macérais to coalesce into globules and veins without increasing the reflectance or causing vesiculation of the resinite. On the basis of infrared spectral properties and carbonization behavior Murchison (14) was able to divide the resinite macérais into two types — one type occurring only in coals of sub-bituminous rank or lower and the other type occurring in bituminous coals. He also noted that much of the resinite in bituminous coals occurred as interconnected globules and veins and he concluded that this was of secondary origin (15). Fusinized or charred resinites observed petrographically in a rod-like form (rodlets) have been reported in Illinois coals (16) and in other areas (17-18). Occurrence Resinite macérais are found in coals from all of the major coalfields in the United States and they are particularly abundant in the coals of the Wasatch Plateau in Utah. Although no national pétrographie data base exists for American coals, the Perm State Coal Data Base is the best collection of information on a representative selection of U. S. coals. With the help of Mr. David Glick from the Coal and Organic Petrology Laboratories at The Pennsylvania State University, data on the occurrence of resinite was compiled. The data included were restricted by sample type (either whole seam or run of mine samples), by rank (vitrinite reflectance less than 1.0 %), and by sample availability. For summaries by seam only the results of seams having more than one sample were included. In Figure 1 the data for the mean resinite content in white light by province is shown. All provinces have less than 1% resinite and the mean for all provinces based on 219 samples is about 0.5 %. In Figure 2 the data for the mean resinite content in blue light by province is shown. All provinces have higher amounts than in white light and the mean for all provinces based on 65 samples is about 1.25% which is 150% higher. The phenomenon of the detection of higher amounts in blue light is common to all liptinite macérais and is well known and widely reported. Even though the data base is limited by both number of seams and number of samples per seam, it is still instructive to break the data down by seam (Figure 3), where it is easily seen that the seams from the Rocky Mountain Provence are the richest in resinite. In addition to the Penn State Data Base, the Illinois State Geological Survey (ISGS) has an important collection of pétrographie data on coals of the Illinois Basin. Analyses of hundreds of coal samples from all parts of the Illinois Basin show a resinite content of from less than one percent to more than four percent by volume (19). With the help of Dr. Richard Harvey of the ISGS, data on the occurrence of resinite was compiled for the three most commercially important seams in the basin. This data presented in Figure 4 shows that both the Herrin No. 6 (125 samples ) and the Springfield No. 5 (62 samples) seams average more than 1% resinite in blue light and the Colchester No. 2 seam (36 samples) averages less than 0.5%. Even though these data show that resinite is only a minor component of most U. S. coals, it is interesting to note that this amount represents a large resource. For example, when one considers that the state of Illinois has the largest demonstrated reserves of bituminous coal in the U.S.,


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AMBER, RESINITE, AND FOSSIL RESINS


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Figure 2. Average occurrence of resinite macérais by coal provence by blue light petrography. The data are from the Penn State Data Base and are restricted by sample type (either whole seam or run of mine samples) and by rank (vitrinite reflectance less than 1.0 %). Note that the resinite content in all provinces is higher than in white light.


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Figure 3. Average occurrence of resinite macérais by seam by blue light petrography. The data are from the Penn State Data Base and are restricted by sample type (either whole seam or run of mine samples) and by rank (vitrinite reflectance less than 1.0 %). Note that the resinite content is highest in the Rocky Mountain Province.

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scaled for intensity Figure 5. Fluorescence spectra of resinites from the Lower Kittanning seam at different ranks (vitrinite reflectance 0.60% -1.59%). All spectra were determined under the same conditions and are scaled for peak intensity. Note the intensity maximum at 0.72 % reflectance and the decrease at higher ranks.


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about 65 billion tons, it is a simple calculation to determine that there is a great reserve of resinite in the state. Although the resinite in Illinois has not been exploited commercially, resinite has been exploited with success in the western U.S., especially in the Wasatch Plateau coalfields of Utah. Recent work by Miller and his colleagues at the University of Utah (supported by the USDOE) has shown successful pilot-plant proof-of-concept testing in the recovery of resinite. He points out that the resinitefromthe Wasatch Plateau has been used commercially "in the ink, adhesive, rubber, varnish, enamel, paint and coatings, and thermoplastics industries." and of the solvent refined resinite "This product, at the present time, has a market value of at least $1.00/kg as a chemical commodity ..." (20, p. 420). Petrography Primary Resinite. Because resin, the precursor of the maceral resinite, occurs in the original plant material as a fluid secretion, it has no distinct fossil plant (phyteral) morphology such as the linear aspect of cutinite or the bilateral symmetry of sporinite. The dominant form of resinite is a structureless oblate spheroid often described more simply as a blob, bleb, lump, lens, ovoid, globule etc. In coal samples where woody cell structure has been preserved, resinite can commonly be seen in place as a cell filling (Plate 1 A&B) . This kind of occurrence clearly represents its original botanical affinity. However, it is also common to find the resinite occurring in the matrix of the coal freed from enclosing cell walls (Plate 1 C&D, Plate 2 A-D, Plate 3 A-D). The boundaries of the resinite in the matrix can be both regular (Plate 1 C&D, Plate 2 A&B) and irregular (Plate 2 C&D Plate 3 A&B) as well as sharp (Plate 1 C&D, Plate 2 A-D) and diffuse (Plate 3 A&C). Resinite is very resistant to weathering and biochemical degradation and can therefore be concentrated by such processes. In fact, it is often observed that the coal matrix has compacted around isolated resinite bodies. Because the resinite described above is incorporated into the peat precursor of the coal in the initial stages of formation, these occurrences of resinite are considered primary. Reflected Light. In reflected white light resinite appears to be gray with a reflectance darker than the vitrinite in the same sample but usually slightly brighter than the sporinite and cutinite. Sometimes larger particles of resinite are translucent with an orange tint. (Plate 1 C&D). While primary resinites are usually free of noticeable inclusions, pyrite crystals can occasionally be associated with them (Plate 2 A&B). Also it is common for resinites to have a darker outerrimwith a brighter inner core.(Plate 1 C&D). This zoning is usually ascribed to weathering or oxidation. Fluorescent Light. In fluorescence microscopy resinites usuallyfluorescevery well. Two types of illumination are used, ultra-violet with a narrow range of excitation around 365 nm used for spectral analysis and blue light with a broader excitation range peaking around 400 nm for survey viewing. The intensity of thefluorescenceis usually highest in the lower end of the bituminous range (0.5-0.75 % vitrinite reflectance) and it decreases with increasing rank. Figure 5 shows a typicalfluorescenceintensity variation for a rank series of samplesfromthe Lower Kittanning seam. It is different from most other seams in that fluorescence could be detected above a vitrinite reflectance of 1.40%. N O T E : Plate 1 appears on page 225; Plate 2 appears on page 226; Plate 3 appears on page 227.



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Thefluorescencecolor is usually a bright yellow in the high- volatile bituminous rank range, although it can rangefrombluish green to reddish orange. In any given coal the fluorescence color shifts toward the red end of the spectrum with increasing rank. At any given rank the resinite macérais in a sample will usually have spectra of similar shape although the position of the peaks can vary. In Appalachian and midwestern U.S. coals this variation is most often restricted, but in western U. S. coals the variation can be extreme, as shown in Figure 6. Three of the factors that account for this variation are the original resinite chemistry, the degree of weathering or oxidation the macérais have experienced, and the degree of coalification (rank). Studies of the spectra of resinite macérais of coals from Utah, Wyoming, New Mexico, and Colorado (7-10,22-24) and the Canadian Rockies (25) have shown that the resinite macérais can be statistically divided into four orfivegroups. However, when the spectra are plotted on the C. I. E. chromaticity diagram based on chromaticity parameters, the distribution is continuous. An example for spectra taken in both ultraviolet and blue light from a Hiawatha seam sample is given in Figure 7. In addition to the pétrographie features detailed above, the primary resinite macérais of western U. S. coals and particularly those of the Wasatch Plateau in Utah very commonly show other features such as brittle fracture (Plate 4 D), multiple-layer zoning (Plate 3 D), flow textures (Plate 3 C, Plate 4 C), multi-phase textures (Plate 3 B&D), and minor vesiculation. Secondary Resinite. As much as 50-60 % of the resinite in western coals can occur in cleat andfracturefillingsand is, thus, a post-depositional or secondary occurrence. This resinite has been mobilized to flow into cleats and fractures at some point in the geological coalification history of the coal. The source of the resinite must be the same as that for the primary resinite, the resins in the original plant material. No evidence for a source outside of the coal seams has ever been reported. Reflected Light. In reflected white light the secondary resinite appears similar to primary resinite except for its planar (vein-like) nature and obvious inclusions of coal fragments. These xenoliths were picked up during the intrusive flow of the resinite. The reflectance of these macérais is the same dark gray of the primary resinite macérais. This and their brittlefracturedistinguishes them from the void-like blackness of exsudatinite, another void filling secondary maceral believed to be an oil-like exudation generated during coalification (26-29). Fluorescent Light. In fluorescence microscopy the secondary resinites also fluoresce very well. The fluorescence color variesfrombluish green to reddish orange. The planar cleat filling form is usually very evident. The boundaries of thefillingswith the coal mass can be clean and sharp or brecciated. In addition to coal xenoliths (Plate 4 A&B), other evidence of flow can be seen in swirl textures (Plate 3 C, Plate 4 C) and multi-layer zoning (Plate 3 D). The multi-layer zoning suggests multiple episodes of resinite emplacement and this suggestion is supported by cross-cutting relationships of the fillings or veins. An outstanding feature of all of the fillings is the abundance of opaque inclusions which range in sizefromfragments showing plant cell structure to dust (Plate 3 A-D, Plate 4 C&D). It is this micron to sub-micron material that defines most of the zoning and flow textures. N O T E : Plate 4 appears on page 228.


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Plate 1. Photomicrographs of resinite macérais: A. Resinite macérais filling cell structures in vitrinite, derived from the original occurrence in the plant precursors (Elkhorn No. 3 seam - white light); B. Same field as A in blue light showing the fluorescence of the resinite; C. Typical resinite ovoid with internal reflections and orange color (Herrin No. 6 seam - white light); D. samefieldas C in blue light. Note the darker outer rim.




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Plate 2. Photomicrographs of resinite macérais: A. Resinite lenses with bright pyrite crystals concentrated in center (Herrin No. 6 seam - white light); B. Same field as A in blue light showing the fluorescence of the resinite and non-fluorescent pyrite; C. Resinite ovoid with irregular boundaries (Herrin No. 6 seam - white light); D. same field as C in blue light.


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Plate 3. Photomicrographs of resinite macérais: A. Resinite lens showing zoning with a bright rim and dark core (Hiawatha seam - blue light); B. Portion of a resinite lens showing zoning with a bright rim and dark core which contains nonfluorescent inclusions and yellow droplets (Hiawatha seam - blue light); C. Irregular resinite body showing both zoning and flow texture (Hiawatha seam blue light); D. Resinite mass showing multi-layer zoning.




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Plate 4. Photomicrographs of resinite macérais: A. Resinite cleat filling including a coal xenolith (Hiawatha seam - white light); B. Same field as A in blue light; C. Cross-cutting resinite veinlets. Note the flow of the darker veinlet into the brighter one (Hiawatha seam - blue light); D. Cross-cutting resinite veinlets. Note the brittle fracture of larger veinlet (Hiawatha seam - blue light).



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Figure 6. Fluorescence spectra of resinites from the Hiawatha seam (Wasatch Plateau) scaled to peak intensity. All spectra were taken under the same conditions from different resinite macérais in the same sample. The shift in the peaks represent a color changefromblue to orange.




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Figure 7. Chromaticity (CLE., 1931) plot in both ultra-violet and blue light of resinite spectrafromthe Hiawatha seam, Utah. Note the continuous distribution.


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Summary Resinite macérais are ubiquitous, though minor, components in most American coals below medium-volatile bituminous rank. Resinite macérais have two common modes of occurrence. In most Appalachian and mid-western U. S. coal seams of Carboniferous age resinites occur as primary (present at the time of deposition) ovoid bodies. In coals from the western U. S. of Cretaceous/Tertiary age, much of the resinite occurs as secondary cleat and fissure fillings. This secondary resinite shows an intrusive relationship to the host coal and often showsflowtexture and carries xenoliths of coal in resinite veinlets. Acknowledgments The author is pleased to acknowledge the assistance of Mr. David Glickfromthe Coal and Organic Petrology Laboratories at The Pennsylvania State University and Dr. Richard Harvey of the Illinois State Geological Survey with the data bases. The assistance of Dr. David Bensley of the Coal Characterization Laboratory in the Department of Geology at Southern Illinois University with the photomicrographs and fluorescence spectra is also gratefully acknowledged. Literature Cited 1. 2. 3. 4. 5. 6. 7.

8. 9.

10.

White, D., 1914, Resins in Paleozoic plants and in coals of high rank:USGS Professional Paper 85, p. 65-83. Spieker, E.M., and Baker, Α. Α., 1928, Geology and coal resources of Salina Canyon district, Sevier County, Utah: U.S. Geol. Survey Bull. 796-C, p. 125-170. Tomlinson, H., 1932, Falls of roof and coal in the Book Cliffs and Wasatch Plateau coalfields of Utah: U.S. Bur. Mines Rept. of Inv. 3189, 91p. Thiessen, Reinhardt and Sprunk, G. C., 1937, Origin and petrographic composition of the Lower Sunnyside coal of Utah: U. S. Bur. of Mines Tech. Paper 573, 34p. Selvig, W.A., 1945. Resins in coal. U.S. Bureau of Mines Tech. Paper 680, 24p. Buranek, A.M., and Crawford, A.L., 1952, Notes on resinous coals of Utah: Utah Geol. and Mineralog. Survey Monograph Series, No. 2, p. 3-9. Crelling, John C., Dutcher, Russell R. and Lange, Rolf V., 1982, Petrographic andfluorescenceproperties of resinite maceralsfromwestern U.S. coals: Proceedings of the Fifth Symposium on the Geology of Rocky Mountain Coal 1982, ed. Klaus D. Gurgel, Bulletin 118, Utah Geological and Mineral Survey, p. 187-191. Crelling, JohnC.,1982, Current uses offluorescencemicroscopy in coal petrology: Jour. of Microscopy. v. 132, part 3, p. 251-266. Teerman, StanC.,Crelling, JohnC.,and Glass, Garry B., 1987, Fluorescence spectral analysis of resinite macerals from coals of the Hanna Formation, Wyoming, U.S.A.: Int. Jour. of Coal Geology v. 7, p. 315-334. Crelling, John C., Pugmire, Ronald J., Meuzelaar, Henk L.C., McClennen, William H., Huaying Huai, and Karas, Jirina, 1991, Chemical structure and petrography of resinite from the Hiawatha "B" coal seam: Energy and Fuels, v. 5, no. 5, p. 668-694.


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Murchison, D.G., and Jones, J.M., 1963, Properties of the coal macerals: elementary composition of resinite: Fuel, v. 42, p. 141-157. Jones, J.M., and Murchison, D.G., 1963, The occurrence of resinite in bituminous coals: Economic Geology, v. 58, no. 2, p. 263-273. Murchison, D.G., Jones, J.M., 1964, Resinite in bituminous coals: Adv. in Organic Geochemistry, Proceedings of the International Meeting, Milan, 1962: Pergamon Press, London p. 1-21. Murchison, D.G., 1966, Infrared Spectra of Resinites and their Carbonized and Oxidized Products: Coal Science, Adv. Chem. Ser. 55, p. 307-331. Murchison, D.G., 1976, Resinite: Its Infrared Spectrum and Coalification Pattern: Fuel, v. 55, p. 79-83. Kosanke, R.M., and Harrison, J.A., 1957, Microscopy of the Resin Rodlets of Illinois Coal: Ill. Geol. Surv. Circ. 234, p. 1-14. Lyons, PaulC.,Hatcher, Patrick G., Minkin, Jean Α., Thompson, Carolyn L., Larson, Richard R., Brown, Zoe Α., Pheifer, Raymond N., 1984, Resin rodlets in shale and coal (lower Cretaceous), Baltimore canyon trough: Int. Jour. Coal Geology, v. 3, p. 257-278. Lyons, PaulC.,Hatcher, Patrick G., and Brown, Floyd W., 1986, Secretinite: a proposed new maceral of the inertinite maceral group: Fuel, v. 65, no. 8, p. 10941098. Harvey, Richard D., Crelling, JohnC.,Dutcher, Russell R. and Schleicher, John Α., 1979, Petrology and related chemistry of coals in the Illinois Basin: in Depositional and Structural history of the Pennsylvanian System in the Illinois Basin, Part 2: invited papers, eds., James E. Palmer and Russell R. Dutcher, IX Inter. Carboniferous Congress, Urbana, Illinois Geological Survey, p. 127-142. Miller, J. D., Jensen, G.F., Yu, Q, and Ye, Y, 1992, Selectiveflotationof fossil resinites from western coal: Proceedings - Eighth Ann.Coal Preparation, Utilization, and Environmental Control Contractors Conference, USDOE- PETC, Pittsburgh, PA, p. 420-427. Yu, Q., Bukka, K., Ye, Y., and Miller, J.D., 1991, Characterization of resin types from the Hiawatha seam of the Wasatch Plateau coalfield:Fuel Proc. Tech., v. 28, p. 105-118. Crelling, John C. and Bensley, David F., 1984, Characterization of coal macerals byfluorescencemicroscopy: in Chemistry and Characterization of Coal Macerals, ed. Randall E. Winanas and John C. Crelling, American Chemical Society Symposium Series 252, American Chemical Society, Washington, D.C., p. 33-45. Pasley, Mark Α., and Crelling, JohnC.,1988, Fluorescent spectral types of selected Colorado bituminous coals: Organic Geochemistry, v. 12, no. 4, p. 333343. Bensley, David F., and Crelling, JohnC.,1992, In-situ microspectrophotometry of coalmacerals:Advances in Coal Spectroscopy: Ed. H.L.C. Meuzelaar, Plenum Press, New York, p. 119-139. Dobell, P., Cameron, A. R., and Kalkreuth, W. D., 1984, Petrographic examination of low rank coals from Saskatchewan and British Columbia, Canada, including reflected andfluorescentlight microscopy, SEM, and laboratory oxidation procedures: Can. J.Earth Sci., v. 21, p.1209-1228.


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Teichmüller M., 1974a, Uber neue Macerale der Liptinite-Gruppe und die Entstehung des Micrinits: Fortschr. Geol. Rheinl. Westfalen, v. 24, p. 37-64. Teichmüller, M., 1974b, Entstehung und Veranderung bituminoser Substanzen in Kohlen in Beziehung zur Entstehung und Umwandlung des Erdols: Fortschr. Geol. Rheinl. Westfalen, v. 24, p. 65-112. Teichmüller M., 1974c., Generation of petroleum-like substances in coal seams as seen under the microscope: In: B. Tissot and F. Bienner (Eds), Advances in Organic Geochemistry, 1973. Technip, Paris, p. 379-407. Teichmüller M. and Durand Β., 1983, Fluorescence microscopical rank studies on liptinites and vitrinites in peat and coals, and comparison with the results of the Rock-Eval pyrolysis: Int. J. Coal Geol., v. 2, p. 197-230.


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