ISO 7404-4:2017

INTERNATIONAL ISO
STANDARD 7404-4
Second edition
2017-08
Methods for the petrographic analysis
of coals —
Part 4:
Method of determining
microlithotype, carbominerite and
minerite composition
Méthodes d’analyse pétrographique des charbons —
Partie 4: Détermination de la composition en microlithotypes,
carbominérites et minérites
Reference number
ISO 7404-4:2017(E)
©
ISO 2017

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ISO 7404-4:2017(E)

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ISO 7404-4:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Material . 2
6 Apparatus . 2
7 Procedure. 3
8 Expressions of results . 5
9 Precision . 7
9.1 Repeatability limit . 7
9.2 Reproducibility limit . 7
10 Test report . 8
Bibliography . 9
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ISO 7404-4:2017(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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different types of ISO documents should be noted. This document was drafted in accordance with the
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URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee TC 27, Solid mineral fuels, Subcommittee SC 5,
Methods of analysis.
This second edition cancels and replaces the first edition (ISO 7404-4:1988), which has been technically
revised.
A list of all the parts in the ISO 7404 series can be found on the ISO website.
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ISO 7404-4:2017(E)

Introduction
Petrographic analyses have been recognized internationally as important in the context of the
genesis, vertical and lateral variation, continuity, metamorphism and usage of coal. The International
Committee for Coal Petrology (ICCP) has made recommendations concerning nomenclature and
analytical methods and has published and described in detail the characteristics of a wide range of
coals. This document agrees substantially with the text of relevant ICCP publications and incorporates
many useful comments made by members of the ICCP and by member bodies of ISO/TC 27.
Petrographic analyses of a single coal provide information about the rank, the maceral and
microlithotype compositions and the distribution of mineral matter in the coal. The reflectance of
vitrinite is a useful measure of coal rank and the distribution of the reflectance of vitrinite in a coal
blend, together with a maceral group analysis, can provide information about some important chemical
and technological properties of the blend.
The ISO 7404 series is concerned with the methods of petrographic analysis currently employed in
characterizing coal in the context of its technological and/or geological use. It establishes a system for
petrographic analysis and comprises five parts, see ISO website:
Microlithotypes are the naturally occurring associations of macerals which characterize the
microscopically visible different types of coal. By convention, the identity of a microlithotype is
determined by the maceral group or groups occurring within an area of at least 50 μm × 50 μm and
which are present in amounts equal to or exceeding 5 % by volume. Hence, they can comprise a single
maceral or maceral group if it exceeds these dimensions. Microlithotypes may include up to 20 % by
volume of minerals such as clay, quartz and carbonates or up to 5 % by volume of sulfide minerals.
If the content of mineral matter exceeds these amounts, the material is designated as minerite or
carbominerite depending on the proportions of coal and mineral matter.
Carbominerites can be subdivided according to the type of mineral matter.
Microlithotypes contribute information on the genesis of coal seams and can assist in solving problems
of seam correlation. Because they determine, together with rank and mineral matter, the hardness
and density of the bulk coal substance, microlithotypes affect the behaviour of coal in mining and coal
preparation processes. The different microlithotypes determine, under given geological conditions, the
distribution of micro-cracks and to some extent the cleat in the coal. The results of maceral analyses can
be interpreted more meaningfully from a knowledge of microlithotype composition. Such information
can assist in explaining the behaviour of coal in commercial and experimental utilization processes
where the association of macerals is known to be important.
NOTE The percentage volume of carbonate, clay and quartz minerals on the one hand and sulfide minerals on
the other, which define the carbominerites and minerites, correspond to the densities which separate acceptable
3
coal from middlings (1,5 g/cm ) and from rejects in coal preparation.
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INTERNATIONAL STANDARD ISO 7404-4:2017(E)
Methods for the petrographic analysis of coals —
Part 4:
Method of determining microlithotype, carbominerite and
minerite composition
1 Scope
This document specifies a method, using a graticule with 20 crossline intersections, for determining the
proportions of microlithotypes, carbominerite and minerite in coals. It applies only to determinations
made on polished particulate blocks using reflected white light (about 400 nm to 700 nm). Additional
blue, blue-violet or UV light excitation (365 nm to 440 nm) for better identification of liptinite in
fluorescence may be used especially at low rank coals.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 7404-1, Methods for the petrographic analysis of coals — Part 1: Vocabulary
ISO 7404-2, Methods for the petrographic analysis of coals — Part 2: Methods of preparing coal samples
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7404-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
point
observation of a portion of the particulate block through the eyepiece graticule made during the
analysis
Note 1 to entry: The allocation of a point to a particular microlithotype, or to carbominerite or minerite, is
determined by the macerals and/or mineral matter present at the 20 intersections of the graticule. A point is only
counted if at least 10 intersections fall on a particle.
4 Principle
Examination by using a reflected light microscope and point count procedure of a representative sample
of coal prepared as a particulate block as described in ISO 7404-2. Identification under an immersion
medium of the microlithotypes from their maceral composition. The proportions of the macerals are
determined using a graticule having a grid with 20 points of intersection spaced to define a distance of
50 μm on the specimen between extreme intersections in the x (abscissa) and y (ordinate) directions,
respectively. The use of such a graticule allows the analyst to comply with the 5 % minimum content
and 50 μm minimum size stipulation.
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ISO 7404-4:2017(E)

5 Material
Immersion medium, having a suitable refractive index and compatibl
...