ASTM D2799-13(2021)e1

Standard Test Method for Microscopical Determination of the Maceral Composition of Coal

SIGNIFICANCE AND USE
5.1 The volume percent of physical components of coal is used as an aid in coal seam correlation and in the characterization of coals for their use in carbonization, gasification, liquefaction, and combustion processes.  
5.2 This test method is for use in scientific and industrial research, not compliance or referee tests.
SCOPE
1.1 This test method covers the equipment and techniques used for determining the physical composition of a coal sample in terms of volume percent of the organic components and of mineral matter, if desired.  
1.2 The term weight is temporarily used in this test method because of established trade usage. The word is used to mean both force and mass and care must be taken to determine which is meant in each case (the SI unit for force is newton and for mass, kilogram).  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Historical
• Publication Date: 31-Mar-2021
• ICS: 73.040 - Coals
• Technical Committee: D05 - Coal and Coke
• Drafting Committee: D05.28 - Petrographic Analysis of Coal and Coke

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D2799 − 13 (Reapproved 2021)
Standard Test Method for
Microscopical Determination of the Maceral Composition of
Coal
This standard is issued under the fixed designation D2799; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial corrections were made throughout in May 2021.
1. Scope and Coke from Coal
D4239 Test Method for Sulfur in the Analysis Sample of
1.1 This test method covers the equipment and techniques
Coal and Coke Using High-Temperature Tube Furnace
usedfordeterminingthephysicalcompositionofacoalsample
Combustion
in terms of volume percent of the organic components and of
E177 Practice for Use of the Terms Precision and Bias in
mineral matter, if desired.
ASTM Test Methods
1.2 The term weight is temporarily used in this test method
E691 Practice for Conducting an Interlaboratory Study to
because of established trade usage. The word is used to mean
Determine the Precision of a Test Method
bothforceandmassandcaremustbetakentodeterminewhich
is meant in each case (the SI unit for force is newton and for
3. Terminology
mass, kilogram).
3.1 Definitions—For definitions of terms, refer to Terminol-
1.3 This standard does not purport to address all of the
ogy D121.
safety concerns, if any, associated with its use. It is the
3.2 Classification—The classification of the microscopic
responsibility of the user of this standard to establish appro-
constituents into groups of similar properties in a given coal is
priate safety, health, and environmental practices and deter-
as follows:
mine the applicability of regulatory limitations prior to use.
Maceral Group Maceral
1.4 This international standard was developed in accor-
Vitrinite —
dance with internationally recognized principles on standard-
Liptinite or (exinite) alginite
ization established in the Decision on Principles for the
cutinite
Development of International Standards, Guides and Recom-
resinite
mendations issued by the World Trade Organization Technical
sporinite
Barriers to Trade (TBT) Committee. Inertinite fusinite
inertodetrinite
macrinite
2. Referenced Documents
micrinite
funginite
2.1 ASTM Standards:
secretinite
D121 Terminology of Coal and Coke
semifusinite
D2797 Practice for Preparing Coal Samples for Microscopi-
cal Analysis by Reflected Light
3.3 Many laboratories associated with the coke-making
D2798 Test Method for Microscopical Determination of the
industry use the following simplified classification for petro-
Vitrinite Reflectance of Coal
graphic analysis of bituminous coal:
D3174 Test Method forAsh in theAnalysis Sample of Coal
vitrinite
liptinite (other than resinite)
resinite
semifusinite
This test method is under the jurisdiction of ASTM Committee D05 on Coal
micrinite
and Coke and is the direct responsibility of Subcommittee D05.28 on Petrographic
fusinite
Analysis of Coal and Coke.
mineral matter
Current edition approved April 1, 2021. Published May 2021. Originally
3.4 Definitions of Terms Specific to This Standard:
approved in 1969. Last previous edition approved in 2013 as D2799 – 13. DOI:
10.1520/D2799-13R21E01.
3.4.1 alginite, n—a liptinite maceral that is generally spheri-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
cal or ovoid, frequently having a crenulated border and
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
somewhat irregular reflectance and sometimes occurring in
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. clusters reflecting an origin from Botryococcus algae.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D2799 − 13 (2021)
3.4.1.1 Discussion—Alginite often occurs as degraded frag- processes and may contain up to several weight percent of
ments derived from colonial or unicellular bodies. inorganic elements in microscopically indistinguishable form.
3.4.10 maceral classification, n—The systematic division of
3.4.2 cutinite, n—a liptinite maceral in the form of a sheet
the organic substances (macerals) in coal based on their
reflecting its origin from leaf- or twig-covering plant cuticle,
appearance in the optical microscopic.
frequently exhibiting reticulation in planar section and a
3.4.10.1 Discussion—Although macerals may be identified
serrated edge in cross section.
in translucent, thin sections using criteria not defined herein,
3.4.3 exinite, n—Deprecated term. Use preferred term lip-
thistestmethoddealsonlywithidentificationandclassification
tinite; sometimes has also been used as a synonym for
based on microscopic appearance on polished surfaces accord-
sporinite.
ing to Practice D2797. Three major maceral groups are
3.4.4 funginite, n—an inertinite maceral occurring as round
recognized on the basis of relative reflectance in white light,
or ovoid bodies, frequently containing voids, reflecting an
specifically: vitrinite—moderately reflecting (intermediate
origin from fungal sclerotia; also occurs (especially in lower
gray), liptinite—poorly reflecting (black to dark gray), and
rank coals) as interlaced, stringy materials derived from fungal
inertinite—highly reflecting (light gray to white). Each group
hyphae.
can be subdivided on the basis of other microscopically
distinctive features such as: reflectance contrasts (relative
3.4.5 fusinite, n—an inertinite maceral distinguished princi-
shades of gray); morphology, that is, shape and size (morpho-
pally by the preservation of some feature(s) of the plant cell
logic distinctions in definitions contained herein are idealized
wall structure, and with a particle size greater than 50 µm
becausemorphologicappearancedependsontheinitialformof
except when it occurs as a fragment within the binder matrix;
the source material, its state of preservation, including
see also semifusinite.
granulation, and on the orientation of the cross section pre-
3.4.6 inertinite, n—macerals that exhibit higher reflectance
sented on the polished preparation); spatial association with
than other organic substances in the coal.
other substances; fluorescence properties (color, intensity) in
3.4.6.1 Discussion—In any coal ranked lower than
bluetoultravioletlight;relief;colortinges;internalreflections;
anthracitic, inertinite reflectance commonly spans the range
and anisotropic properties.
from only slightly higher than associated vitrinite to very high
Microscopic criteria provide classification capability with-
reflectance (often as high as R max ≥ 6 %). In anthracitic rank
out any implication of absolute chemical composition or
o
coals, inertinite reflectance may be lower than that of vitrinite,
physical behavior, although some properties relative to other
and is then recognized by its morphology and form of
macerals in the same coal can be inferred broadly. Substances
anisotropy. Highly reflecting inertinite commonly exhibits
classified as the same maceral by microscopic criteria can
relief on polished surface. Its name derives from the fact that
differ chemically, physically, and behavioristically in coals of
most varieties behave inertly in the thermoplastic deformation
different ranks. Some properties can be estimated by the
during the coking process (except in its lowest reflecting
measurement of reflectance (Test Method D2798).
manifestation). The volatile matter yield of inertinite is lower
See 3.3 for the classification used by most practitioners of
than that of other macerals in the same coal.
this test method.
3.4.11 macrinite, n—an inertinite maceral, generally
3.4.7 inertodetrinite, n—an inertinite maceral occurring as
individual, angular, clastic fragments incorporated within the nonangular, exhibiting no relict plant cell wall structure and
larger than 10 µm.
matrix of other macerals (commonly vitrinite) or minerals, and
in the size range from 2 µm to 50 µm.
3.4.12 micrinite, n—an inertinite maceral, generally
nonangular, exhibiting no relict plant cell wall structure,
3.4.8 liptinite, n—macerals that exhibit lower reflectance
smaller than 10 µm and most commonly occurring as particles
thanotherorganicsubstancesinacoal,appearingblacktodark
around 1- to 5-µm diameter.
gray and that fluoresce under blue to ultraviolet light in coals
ranked high volatile bituminous and lower.
3.4.13 mineral matter, n—in coal, historically considered to
3.4.8.1 Discussion—The fluorescence of liptinite distin- be the non-organic fraction composed of physically discrete
particles of minerals, such as clays, quartz, pyrite, etc., and all
guishes fine-grained liptinite from similar sized, low
reflectance, nonfluorescing clay minerals. Liptinite is derived elements other than, carbon, hydrogen, oxygen, nitrogen, and
sulfur in the organic fraction.
principally from lipid substances forming skins (exines) and
resinous secretions or exudates of plants. Liptinite is sub-
3.4.14 resinite, n—a liptinite maceral occurring as rounded,
classified on the basis of morphology inherited from plant
ovoid, or rod-like bodies assuming the shape of an enclosing
structure. In coals in which vitrinite reflectance exceeds about
cell lumen or as irregular shapes filling cracks in the coal.
1.4 %,liptinitecanbeindistinguishablefromvitrinite.Liptinite
3.4.15 secretinite, n—an inertinite maceral occurring as
has the highest volatile matter yield of the macerals in a coal.
round, ovoid, or oblong bodies, without obvious plant
3.4.9 maceral, n—an organic substance in coal that is
structure, vesicled to non-vesicled, sometimes containing char-
distinguishedandclassified(see maceral classification)onthe
acteristic fractures, slits, or a notch.
basis of its optical microscopic properties.
3.4.15.1 Discussion—Secretinite is considered to be derived
3.4.9.1 Discussion—Macerals originate from plant tissues, by the oxidation of plant resin secretions or humic gels.
secretions, and exudates that have been altered by geological Vesicular and non-vesicular secretinite was formerly included
´1
D2799 − 13 (2021)
in sclerotinite of fungal origin. Secretinite is a common components are determined on a surface section of a sample.
maceral in medium- and high-rank Permian and Carboniferous However, the area and volume proportions are the same when
coals. the components are randomly distributed throughout the
sample.
3.4.16 semifusinite, n—an inertinite maceral with morphol-
4.1.1 Color photomicrographs of the maceral components
ogy like fusinite sometimes with less distinct evidence of
ofbituminouscoalsareavailablefromvariouspublicationsand
cellular structure, but with reflectance ranging from slightly
websites.
greater than that of associated vitrinite to some value interme-
diate to that of the brightest fusinite. The particle size is also
5. Significance and Use
greater than 50 µm except when it occurs as a fragment within
5.1 The volume percent of physical components of coal is
the binder matrix.
used as an aid in coal seam correlation and in the character-
3.4.16.1 Discussion—The precise reflectance boundary be-
ization of coals for their use in carbonization, gasification,
tween semifusinite and fusinite has not been universally
liquefaction, and combustion processes.
defined, although some practitioners place the division at
R max = 2.0 %; hence, semifusinite is somewhat vaguely de-
o 5.2 This test method is for use in scientific and industrial
fined as “fusinite with low reflectance.”
research, not compliance or referee tests.
3.4.17 sporinite, n—a liptinite maceral exhibiting various
6. Apparatus
lenticular, oval, or round forms that reflect the cross-sectioning
of a flattened, hollow, ovoid body; sometimes exhibits rod-like
6.1 Microscope—Any microscope with a mechanical stage
projections that are small relative to the size of the total body.
and a vertical illuminator (that is, metallurgical or opaque-ore
3.4.17.1 Discussion—Sporinite originated as a lipid sub-
microscope) may be used, provided that the lens combination
stance that covered, as a skin, ovoid spore or pollen grains
of objective and eyepiece permits resolution of objects on the
which commonly ranged from around ten to several hundred
order of 1 µm to 2 µm. A minimum magnification of approxi-
micrometres in diameter. Sporinite often occurs as fragments
mately 400 diameters is recommended. Either a prism or a
derived from these initially ovoid bodies.
partially reflecting glass plate may be used in the illuminator.
One eyepiece of the microscope should be fitted with a
3.4.18 vitrinite, n—the predominant maceral in most coals
graticule or crosshair.
of intermediate reflectance occurring as substantial volumes of
6.1.1 Eyepiece Disk—If other than crosshairs are used, the
more or less uniformly reflecting material or as a matrix
eyepiece disk shall contain a Whipple graticule or one of such
enclosing particles of other macerals and mineral matter or as
design that four points are visible, lying at the corners of a
particles or bands intermixed with other maceral fragments.
square covering nearly all of the field of view. The minimum
3.4.18.1 Discussion—Becausemostvitriniteisderivedfrom
effective distance between the points, referred to the plane of
thecellular,structuraltissuesofplants,itmayexhibitrelictcell
the specimen, shall be 0.1 mm.
structure. The reflectance of vitrinite is related to the rank of
6.1.2 Mechanical Stage—The mechanical stage shall be of
the coal in which it is found. Reflectance increases (from
such type that the specimen can be quickly advanced by
around R max = 0.3 % in lignitic coals) in parallel with the
o
definite fixed increments in two perpendicular directions. If an
increase in fixed carbon yield associated with increasing rank.
electrically operated stage is used, increment steps in one
Because many of the properties of typical coals reflect the
direction across the specimen may be actuated by the counter
properties of the dominating vitrinite, it is common practice to
switches.
estimate coal properties and process behaviors by measuring
the reflectance of a representative sampling of vitrinite in the
6.2 Counter—Counters shall be used to count components.
specimen according to procedures described in Test Method
D2798. 7. Test Specimen
Pseudovitrinite, a certain variety of vitrinite, is differentiated
7.1 Prepare sample briquets in accordance with Practice
by some practitioners. It exhibits slightly higher reflectance
D2797.
than most of the vitrinite in the coal and is commonly slitted,
with indistinct remnant cell structure and angular or jagged
8. Procedure
ed
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D2799 − 13 D2799 − 13 (Reapproved 2021)
Standard Test Method for
Microscopical Determination of the Maceral Composition of
Coal
This standard is issued under the fixed designation D2799; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial corrections were made throughout in May 2021.
1. Scope
1.1 This test method covers the equipment and techniques used for determining the physical composition of a coal sample in terms
of volume percent of the organic components and of mineral matter, if desired.
1.2 The term weight is temporarily used in this test method because of established trade usage. The word is used to mean both
force and mass and care must be taken to determine which is meant in each case (the SI unit for force is newton and for mass,
kilogram).
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D121 Terminology of Coal and Coke
D2797 Practice for Preparing Coal Samples for Microscopical Analysis by Reflected Light
D2798 Test Method for Microscopical Determination of the Vitrinite Reflectance of Coal
D3174 Test Method for Ash in the Analysis Sample of Coal and Coke from Coal
D4239 Test Method for Sulfur in the Analysis Sample of Coal and Coke Using High-Temperature Tube Furnace Combustion
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—For definitions of terms, refer to Terminology D121.
This test method is under the jurisdiction of ASTM Committee D05 on Coal and Coke and is the direct responsibility of Subcommittee D05.28 on Petrographic Analysis
of Coal and Coke.
Current edition approved Jan. 1, 2013April 1, 2021. Published March 2013May 2021. Originally approved in 1969. Last previous edition approved in 20122013 as
D2799 – 12.D2799 – 13. DOI: 10.1520/D2799-13.10.1520/D2799-13R21E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D2799 − 13 (2021)
3.2 Classification—The classification of the microscopic constituents into groups of similar properties in a given coal is as follows:
Maceral Group Maceral
Vitrinite —
Liptinite or (exinite) alginite
cutinite
resinite
sporinite
Inertinite fusinite
inertodetrinite
macrinite
micrinite
funginite
secretinite
semifusinite
3.3 Many laboratories associated with the coke-making industry use the following simplified classification for petrographic
analysis of bituminous coal:
vitrinite
liptinite (other than resinite)
resinite
semifusinite
micrinite
fusinite
mineral matter
3.4 Definitions of Terms Specific to This Standard:
3.4.1 alginite, n—a liptinite maceral that is generally spherical or ovoid, frequently having a crenulated border and somewhat
irregular reflectance and sometimes occurring in clusters reflecting an origin from Botryococcus algae.
3.4.1.1 Discussion—
Alginite often occurs as degraded fragments derived from colonial or unicellular bodies.
3.4.2 cutinite, n—a liptinite maceral in the form of a sheet reflecting its origin from leaf- or twig-covering plant cuticle, frequently
exhibiting reticulation in planar section and a serrated edge in cross section.
3.4.3 exinite, n—Deprecated term. Use preferred term liptinite; sometimes has also been used as a synonym for sporinite.
3.4.4 funginite, n—an inertinite maceral occurring as round or ovoid bodies, frequently containing voids, reflecting an origin from
fungal sclerotia; also occurs (especially in lower rank coals) as interlaced, stringy materials derived from fungal hyphae.
3.4.5 fusinite, n—an inertinite maceral distinguished principally by the preservation of some feature(s) of the plant cell wall
structure, and with a particle size greater than 50 μm except when it occurs as a fragment within the binder matrix; see also
semifusinite.
3.4.6 inertinite, n—macerals that exhibit higher reflectance than other organic substances in the coal.
3.4.6.1 Discussion—
In any coal ranked lower than anthracitic, inertinite reflectance commonly spans the range from only slightly higher than associated
vitrinite to very high reflectance (often as high as R max ≥ 6 %). In anthracitic rank coals, inertinite reflectance may be lower than
o
that of vitrinite, and is then recognized by its morphology and form of anisotropy. Highly reflecting inertinite commonly exhibits
relief on polished surface. Its name derives from the fact that most varieties behave inertly in the thermoplastic deformation during
the coking process (except in its lowest reflecting manifestation). The volatile matter yield of inertinite is lower than that of other
macerals in the same coal.
3.4.7 inertodetrinite, n—an inertinite maceral occurring as individual, angular, clastic fragments incorporated within the matrix of
other macerals (commonly vitrinite) or minerals, and in the size range from 22 μm to 50 μm.
´1
D2799 − 13 (2021)
3.4.8 liptinite, n—macerals that exhibit lower reflectance than other organic substances in a coal, appearing black to dark gray and
that fluoresce under blue to ultraviolet light in coals ranked high volatile bituminous and lower.
3.4.8.1 Discussion—
The fluorescence of liptinite distinguishes fine-grained liptinite from similar sized, low reflectance, nonfluorescing clay minerals.
Liptinite is derived principally from lipid substances forming skins (exines) and resinous secretions or exudates of plants. Liptinite
is sub-classified on the basis of morphology inherited from plant structure. In coals in which vitrinite reflectance exceeds about
1.4 %, liptinite can be indistinguishable from vitrinite. Liptinite has the highest volatile matter yield of the macerals in a coal.
3.4.9 maceral, n—an organic substance in coal that is distinguished and classified (see maceral classification) on the basis of its
optical microscopic properties.
3.4.9.1 Discussion—
Macerals originate from plant tissues, secretions, and exudates that have been altered by geological processes and may contain up
to several weight percent of inorganic elements in microscopically indistinguishable form.
3.4.10 maceral classification, n—The systematic division of the organic substances (macerals) in coal based on their appearance
in the optical microscopic.
3.4.10.1 Discussion—
Although macerals may be identified in translucent, thin sections using criteria not defined herein, this test method deals only with
identification and classification based on microscopic appearance on polished surfaces according to Practice D2797. Three major
maceral groups are recognized on the basis of relative reflectance in white light, specifically: vitrinite—moderately reflecting
(intermediate gray), liptinite—poorly reflecting (black to dark gray), and inertinite—highly reflecting (light gray to white). Each
group can be subdivided on the basis of other microscopically distinctive features such as: reflectance contrasts (relative shades
of gray); morphology, that is, shape and size (morphologic distinctions in definitions contained herein are idealized because
morphologic appearance depends on the initial form of the source material, its state of preservation, including granulation, and on
the orientation of the cross section presented on the polished preparation); spatial association with other substances; fluorescence
properties (color, intensity) in blue to ultraviolet light; relief; color tinges; internal reflections; and anisotropic properties.
Microscopic criteria provide classification capability without any implication of absolute chemical composition or physical
behavior, although some properties relative to other macerals in the same coal can be inferred broadly. Substances classified as the
same maceral by microscopic criteria can differ chemically, physically, and behavioristically in coals of different ranks. Some
properties can be estimated by the measurement of reflectance (Test Method D2798).
See 3.3 for the classification used by most practitioners of this test method.
3.4.11 macrinite, n—an inertinite maceral, generally nonangular, exhibiting no relict plant cell wall structure and larger than 10
μm.
3.4.12 micrinite, n—an inertinite maceral, generally nonangular, exhibiting no relict plant cell wall structure, smaller than 10 μm
and most commonly occurring as particles around 1- to 5-μm diameter.
3.4.13 mineral matter, n—in coal, historically considered to be the non-organic fraction composed of physically discrete particles
of minerals, such as clays, quartz, pyrite, etc., and all elements other than, carbon, hydrogen, oxygen, nitrogen, and sulfur in the
organic fraction.
3.4.14 resinite, n—a liptinite maceral occurring as rounded, ovoid, or rod-like bodies assuming the shape of an enclosing cell
lumen or as irregular shapes filling cracks in the coal.
3.4.15 secretinite, n—an inertinite maceral occurring as round, ovoid, or oblong bodies, without obvious plant structure, vesicled
to non-vesicled, sometimes containing characteristic fractures, slits, or a notch.
3.4.15.1 Discussion—
Secretinite is considered to be derived by the oxidation of plant resin secretions or humic gels. Vesicular and non-vesicular
secretinite was formerly included in sclerotinite of fungal origin. Secretinite is a common maceral in medium- and high-rank
Permian and Carboniferous coals.
3.4.16 semifusinite, n—an inertinite maceral with morphology like fusinite sometimes with less distinct evidence of cellular
structure, but with reflectance ranging from slightly greater than that of associated vitrinite to some value intermediate to that of
the brightest fusinite. The particle size is also greater than 50 μm except when it occurs as a fragment within the binder matrix.
´1
D2799 − 13 (2021)
3.4.16.1 Discussion—
The precise reflectance boundary between semifusinite and fusinite has not been universally defined, although some practitioners
place the division at R max = 2.0 %; hence, semifusinite is somewhat vaguely defined as “fusinite with low reflectance.”
o
3.4.17 sporinite, n—a liptinite maceral exhibiting various lenticular, oval, or round forms that reflect the cross-sectioning of a
flattened, hollow, ovoid body; sometimes exhibits rod-like projections that are small relative to the size of the total body.
3.4.17.1 Discussion—
Sporinite originated as a lipid substance that covered, as a skin, ovoid spore or pollen grains which commonly ranged from around
ten to several hundred micrometres in diameter. Sporinite often occurs as fragments derived from these initially ovoid bodies.
3.4.18 vitrinite, n—the predominant maceral in most coals of intermediate reflectance occurring as substantial volumes of more
or less uniformly reflecting material or as a matrix enclosing particles of other macerals and mineral matter or as particles or bands
intermixed with other maceral fragments.
3.4.18.1 Discussion—
Because most vitrinite is derived from the cellular, structural tissues of plants, it may exhibit relict cell structure. The reflectance
of vitrinite is related to the rank of the coal in which it is found. Reflectance increases (from around R max = 0.3 % in lignitic
o
coals) in parallel with the increase in fixed carbon yield associated with increasing rank. Because many of the properties of typical
coals reflect the properties of the dominating vitrinite, it is common practice to estimate coal properties and process behaviors by
measuring the reflectance of a representative sampling of vitrinite in the specimen according to procedures described in Test
Method D2798.
Pseudovitrinite, a certain variety of vitrinite, is differentiated by some practitioners. It exhibits slightly higher reflectance than
most of the vitrinite in the coal and is commonly slitted, with indistinct remnant cell structure and angular or jagged edges.
Pseudovitrinite has been postulated to be less thermoplastic in the coking process.
The term vitrinite is currently used as both a maceral and maceral group.
4. Summary of Test Method
4.1 The components in a representative crushed coal sample, prepared as prescribed in Practice D2797, are identified under a
microscope according to their reflectance, other optical properties, and morphology. The proportions of these components in a
sample are determined by observing a statistically adequate number of points, and summing those representative of each
component. Only area proportions of components are determined on a surface section of a sample. However, the area and volume
proportions are the same when the components are randomly distributed throughout the sample.
4.1.1 Color photomicrographs of the maceral components of bituminous coals are available from various publications and
websites.
5. Significance and Use
5.1 The volume percent of physical components of coal is used as an aid in coal seam correlation and in the characterization of
coals for their use in carbonization, gasification, liquefaction, and combustion processes.
5.2 This test method is for use in scientific and industrial research, not compliance or referee tests.
6. Apparatus
6.1 Microscope—Any microscope with a mechanical stage and a vertical illuminator (that is, metallurgical or opaque-ore
microscope) may be used, provided that the lens combination of objective and eyepiece permi
...