ASTM C1721-22

Standard Guide for Petrographic Examination of Dimension Stone

SIGNIFICANCE AND USE
4.1 Petrographic examinations are made for the following purposes:  
4.1.1 Determine the physical and chemical characteristics (mineralogy, texture, and composition) of the stone specimen that may be observed by petrographic methods and that have a bearing on the performance of the material in its intended use.  
4.1.2 Describe and classify the minerals of the specimen.  
4.1.3 Classify the stone both commercially and geologically based on Terminology C119, recognizing the differences in nomenclature; and based on the following standards, as appropriate:
Specification C406
Specification C503
Specification C568
Specification C615
Specification C616
Specification C629
Specification C1526
Specification C1527  
4.1.4 Determine the relative amounts of the minerals of the specimen and constituents that have a bearing on the performance of the material in its intended use.  
4.1.5 Compare characteristics of the stone with specimens from one or more sources, for which test data or performance records are available.  
4.2 The petrographer should be told in as much detail as necessary, the purposes and objectives of the examination, the kind of information needed, and the extent of examination desired.  
4.2.1 Pertinent background information, including results of prior testing, such as physical and mechanical testing, should be made available. The petrographer’s advice and judgment should be sought regarding the extent of the examination. Available physical and mechanical testing may include the following:
Test Methods C97
Test Method C99
Test Method C170
Test Method C880
Test Methods C120
Test Method C121
Test Method C241
Test Method C1353  
Test Method C217  
4.3 This guide may form the basis for establishing arrangements between a purchaser of consulting petrographic service and the petrographer. In such a case, the purchaser and the consultant should together determine the kind, extent, and objectives of the examination and analy...
SCOPE
1.1 This guide outlines procedures for the petrographic examination of stone specimen material proposed for use as dimension stone used in construction.  
1.2 This guide outlines the extent to which petrographic techniques should be used, the selection of petrographic related properties that should be looked for, and the manner in which such techniques may be employed in the examination of dimension stone.  
1.3 The rock and mineral names given in Terminology C119 should be used, insofar as they are appropriate, in reports prepared in accordance with this guide.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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.  
1.6 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: Published
• Publication Date: 14-Apr-2022
• ICS: 07.060 - Geology. Meteorology. Hydrology
• Technical Committee: C18 - Dimension Stone
• Drafting Committee: C18.01 - Test Methods

Relations

• Refers: ASTM E883-11(2024) - Standard Guide for Reflected–Light Photomicrography
• Effective Date: 01-Apr-2024
• Refers: ASTM C1526-19(2023)e1 - Standard Specification for Serpentine Dimension Stone
• Effective Date: 01-Oct-2023
• Refers: ASTM C119-19 - Standard Terminology Relating to Dimension Stone
• Effective Date: 01-May-2019
• Refers: ASTM C1526-19 - Standard Specification for Serpentine Dimension Stone
• Effective Date: 01-Feb-2019
• Refers: ASTM E883-11(2017) - Standard Guide for Reflected–Light Photomicrography
• Effective Date: 01-Jun-2017
• Refers: ASTM C119-16 - Standard Terminology Relating to Dimension Stone
• Effective Date: 01-May-2016
• Refers: ASTM C1528-15 - Standard Guide for Selection of Dimension Stone
• Effective Date: 01-Mar-2015
• Refers: ASTM C119-14e1 - Standard Terminology Relating to Dimension Stone
• Effective Date: 01-Dec-2014
• Refers: ASTM C119-14 - Standard Terminology Relating to Dimension Stone
• Effective Date: 01-Dec-2014
• Refers: ASTM C1526-08(2014) - Standard Specification for Serpentine Dimension Stone
• Effective Date: 01-Feb-2014
• Refers: ASTM C1528-13 - Standard Guide for Selection of Dimension Stone
• Effective Date: 01-Nov-2013
• Refers: ASTM C1528-12b - Standard Guide for Selection of Dimension Stone
• Effective Date: 01-Oct-2012
• Refers: ASTM C1528-12a - Standard Guide for Selection of Dimension Stone
• Effective Date: 01-Jun-2012
• Refers: ASTM C1528-12 - Standard Guide for Selection of Dimension Stone
• Effective Date: 01-Jan-2012
• Refers: ASTM C119-11 - Standard Terminology Relating to Dimension Stone
• Effective Date: 15-Jun-2011

Overview

ASTM C1721-22: Standard Guide for Petrographic Examination of Dimension Stone establishes a framework for the petrographic analysis of stone materials intended for use as dimension stone in construction. This guide outlines the recommended procedures, extent of analysis, and interpretation needed to assess the mineralogical, physical, and chemical properties that influence the performance and suitability of stone products. Recognized worldwide, this standard supports the evaluation and comparative selection of dimension stone by both commercial and geological classification, thereby aiding in specification, quality control, and risk mitigation for construction and architectural projects.

Key Topics

• Purpose of Petrographic Examination:
  Petrographic investigation determines mineralogy, texture, composition, and other attributes of stone specimens that have a significant impact on the stone's durability and aesthetic appeal.

• Classification and Description:
  Stones are classified and described commercial and geologically using established nomenclature, primarily referencing ASTM Terminology C119 and related specifications.

• Comparative Analysis:
  The guide enables comparison between specimen characteristics and materials with known test data or performance records, supporting informed decision-making.

• Recording and Reporting:
  The guide provides detailed requirements for documentation, including purpose, test procedures, data analysis, and qualitative and quantitative assessments of features affecting stone performance.

• Assessment Focus Areas:

  • Mineral content and proportion
  • Weathered or altered constituents
  • Chemically or physically unstable materials
  • Structural features such as cleavages, foliation, and bedding
  • Surface characteristics and susceptibility to staining, color change, or deterioration from environmental exposure

Applications

• Construction and Architecture:
  Engineers, architects, and builders use petrographic examination to evaluate the integrity, durability, and aesthetic properties of building stone, ensuring suitability for cladding, paving, flooring, and decorative uses.

• Quality Assurance:
  Testing laboratories and consultants employ ASTM C1721-22 to verify that supplied dimension stone materials meet project and industry requirements.

• Material Sourcing and Selection:
  Quarry operators, suppliers, and purchasers utilize the guide to classify stone type, assess variation within quarry sites, identify potential performance issues, and support procurement decisions.

• Failure Analysis and Historic Preservation:
  The guide is invaluable for diagnosing the cause of deterioration in existing stone installations and for informing restoration strategies.

• Regulatory and Specification Compliance:
  Provides standard methodology referenced by contracts, project specifications, and compliance documents.

Related Standards

ASTM C1721-22 is part of a broader suite of ASTM standards for stone evaluation and testing, often used in conjunction with:

• ASTM C406 - Specification for Roofing Slate
• ASTM C503 - Specification for Marble Dimension Stone
• ASTM C568 - Specification for Limestone Dimension Stone
• ASTM C615 - Specification for Granite Dimension Stone
• ASTM C616 - Specification for Quartz-Based Dimension Stone
• ASTM C629 - Specification for Slate Dimension Stone
• ASTM C1526 - Specification for Serpentine Dimension Stone
• ASTM C1527 - Specification for Travertine Dimension Stone
• ASTM C97 - Test Methods for Absorption and Bulk Specific Gravity of Dimension Stone
• ASTM C99 - Test Method for Modulus of Rupture of Dimension Stone
• ASTM C170 - Test Method for Compressive Strength of Dimension Stone
• ASTM C880 - Test Method for Flexural Strength of Dimension Stone
• ASTM C120, C121, C241, C1353, C217 - Various test methods for evaluating physical and mechanical properties

Summary

Adhering to ASTM C1721-22 ensures a thorough, standardized approach to the petrographic examination of dimension stone, supporting the reliable assessment of performance characteristics critical to construction and design. By fostering consistent practices and documentation, this guide helps stakeholders mitigate risk and make informed choices about stone selection and use throughout the life cycle of architectural and infrastructural projects.

Standards Content (Sample)

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.
Designation: C1721 − 22
Standard Guide for
Petrographic Examination of Dimension Stone
This standard is issued under the fixed designation C1721; 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.
1. Scope C120 Test Methods for Flexure Testing of Structural and
Roofing Slate
1.1 This guide outlines procedures for the petrographic
C121 Test Method for Water Absorption of Slate
examination of stone specimen material proposed for use as
C170 Test Method for Compressive Strength of Dimension
dimension stone used in construction.
Stone
1.2 This guide outlines the extent to which petrographic
C217 Test Methods for Weather Resistance of Slate
techniquesshouldbeused,theselectionofpetrographicrelated
C241 Test Method for Abrasion Resistance of Stone Sub-
properties that should be looked for, and the manner in which
jected to Foot Traffic
such techniques may be employed in the examination of
C406 Specification for Roofing Slate
dimension stone.
C503 Specification for Marble Dimension Stone
1.3 TherockandmineralnamesgiveninTerminologyC119 C568 Specification for Limestone Dimension Stone
C615 Specification for Granite Dimension Stone
should be used, insofar as they are appropriate, in reports
prepared in accordance with this guide. C616 Specification for Quartz-Based Dimension Stone
C629 Specification for Slate Dimension Stone
1.4 The values stated in SI units are to be regarded as
C880 Test Method for Flexural Strength of Dimension Stone
standard. No other units of measurement are included in this
C1353 Test Method for Abrasion Resistance of Dimension
standard.
Stone Subjected to Foot Traffic Using a Rotary Platform
1.5 This standard does not purport to address all of the
Abraser
safety concerns, if any, associated with its use. It is the
C1526 Specification for Serpentine Dimension Stone
responsibility of the user of this standard to establish appro-
C1527 Specification for Travertine Dimension Stone
priate safety, health, and environmental practices and deter-
C1528 Guide for Selection of Dimension Stone
mine the applicability of regulatory limitations prior to use.
C1799 Guide to Dimension Stone Test Specimen Sampling
1.6 This international standard was developed in accor-
and Preparation
dance with internationally recognized principles on standard-
E883 Guide for Reflected–Light Photomicrography
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 3. Summary of Guide
mendations issued by the World Trade Organization Technical
3.1 The specific procedures employed in the petrographic
Barriers to Trade (TBT) Committee.
examination of any specimen will depend to a large extent on
the purpose of the examination and the nature of the specimen.
2. Referenced Documents
In most cases the examination will require the use of optical
2.1 ASTM Standards:
microscopy. Complete petrographic examinations for particu-
C97 Test Methods forAbsorption and Bulk Specific Gravity
lar purposes and to investigate particular problems may require
of Dimension Stone
examination of selected constituents by means of additional
C99 Test Method for Modulus of Rupture of Dimension
procedures, such as X-ray diffraction (XRD) analysis for
Stone
crystalline structure and mineral identification, differential
C119 Terminology Relating to Dimension Stone
thermal analysis (DTA) for chemically and physically unstable
minerals, infrared spectroscopy, scanning electron microscopy
(SEM), energy dispersive X-ray analysis (EDX), or other
This guide is under the jurisdiction of ASTM Committee C18 on Dimension
Stone and is the direct responsibility of Subcommittee C18.01 on Test Methods.
procedures.Althoughtheseproceduresarebeyondthescopeof
Current edition approved April 15, 2022. Published May 2022. Originally
this standard, these additional procedures may be more defini-
publishedasC1721-09.Lastpreviouseditionapprovedin2021asC1721-21a.DOI:
tive than visual microscopic methods in certain circumstances.
10.1520/C1721-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.2 Identification of the minerals, composition, rock fabric,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
and structure of a specimen is a necessary step towards
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. recognition of the properties that may be expected to influence
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1721 − 22
the behavior of the material in its intended use, but identifica- be made available. The petrographer’s advice and judgment
tion is not an end in itself. The value of any petrographic should be sought regarding the extent of the examination.
examination will depend to a large extent on the representa- Available physical and mechanical testing may include the
tiveness of the specimens examined, the completeness and following:
accuracy of the information provided to the petrographer Test Methods C97
concerningthesourceandproposeduseofthematerial,andthe Test Method C99
petrographer’s ability to correlate these data with the findings Test Method C170
of the examination. Test Method C880
Test Methods C120
3.3 This guide does not attempt to describe the techniques
Test Method C121
of petrographic work since it is assumed that the guide will be
Test Method C241
used by persons who are qualified by education and experience
Test Method C1353
to employ such techniques for the recognition of the charac-
Test Method C217
teristic properties of rocks and minerals and to describe and
classify the constituents of a specimen that may have an effect
4.3 This guide may form the basis for establishing arrange-
on performance. For some cases, the petrographer will have
ments between a purchaser of consulting petrographic service
had experience adequate to provide detailed interpretation of
and the petrographer. In such a case, the purchaser and the
the petrographic results. For many cases the interpretation will
consultant should together determine the kind, extent, and
be made, in part, by engineers, familiar with the intended use objectives of the examination and analyses to be made, and
of the dimension stone. In other cases, interpretation of the
should record their agreement in writing. The agreement may
findings may require input of others, such as a chemist, stipulatespecificdeterminationstobemade,observationstobe
qualified to relate the observations to the questions to be
reported, funds to be obligated, or a combination of these or
answered. other conditions.
3.4 The petrographer should be familiar with the ASTM
4.4 Petrographicexaminationsprovideidentificationoftype
standards referenced in 2.1.
and varieties of minerals and structures present in the speci-
men. However, as noted above, identification of all minerals
4. Significance and Use
and structures present in the specimen is not necessarily
required.
4.1 Petrographic examinations are made for the following
purposes:
4.5 The petrographic examination should establish whether
4.1.1 Determine the physical and chemical characteristics
the specimen contains chemically unstable minerals or volu-
(mineralogy, texture, and composition) of the stone specimen
metrically unstable materials.
that may be observed by petrographic methods and that have a
4.6 Petrographic examination should identify weathered or
bearing on the performance of the material in its intended use.
otherwise altered constituents or minerals and describe the
4.1.2 Describe and classify the minerals of the specimen.
extent of that weathering or alteration. Where possible, de-
4.1.3 Classify the stone both commercially and geologically
scribe potential aesthetic changes that may occur as a result of
based on Terminology C119, recognizing the differences in
weathering.
nomenclature; and based on the following standards, as appro-
NOTE 1—If the dimension stone will be exposed to freezing and
priate:
thawing and may become wet or saturated in use, finely porous and highly
Specification C406
weatheredorotherwisealteredmineralsshouldbeidentifiedbecausethese
Specification C503
materials will be especially susceptible to damage by freezing and
Specification C568
thawing.
Specification C615
4.7 Petrographic examination should identify constituents
Specification C616
or minerals and the extent to which they may lead to staining
Specification C629
and color change of the surface of the stone when the stone is
Specification C1526
exposed to the weather for exterior use.
Specification C1527
4.1.4 Determine the relative amounts of the minerals of the
4.8 Petrographic examination should identify and estimate
specimen and constituents that have a bearing on the perfor- proportions of constituents that may be susceptible to deterio-
mance of the material in its intended use.
ration from attack by deicing agents where proposed for use at
4.1.5 Compare characteristics of the stone with specimens grade level in freezing environments where deicing salts are
from one or more sources, for which test data or performance anticipated to be used.
records are available.
4.9 Criteria are available for identifying minerals by their
4.2 The petrographer should be told in as much detail as
optical properties or by XRD. Criteria are available for
necessary, the purposes and objectives of the examination, the identifying rocks by their mineral composition and texture.
kind of information needed, and the extent of examination
Examination in both reflected and transmitted light may be
desired. necessary to provide data for these identifications. X-ray
4.2.1 Pertinent background information, including results of microanalysis using energy-dispersive X-ray spectrometers
prior testing, such as physical and mechanical testing, should with scanning electron microscopy (SEM/EDX) or
C1721 − 22
wavelength-dispersive X-ray spectrometers in electron micro- 6.2.1 Notes should be taken during the examination. Each
probes (EMPA/WDX) may provide useful information on the specimen should be described; the relevant features may
chemical composition of minerals and rocks. include the following: shape and dimensions of specimen,
6.2.2 Specimen surface textures and finishes,
4.10 The objectives for which this guide was prepared, will
6.2.3 Crystal or grain size, or both,
have been attained if those involved with the evaluation of the
6.2.4 Internal structure, including observations of preferred
specimen have reasonable assurance that the petrographic
orientation, segregation of grains or crystals, pore space,
examination results, wherever and whenever obtained, may
packing of grains, cementation of grains,
confidently be compared.
6.2.5 Color,
6.2.6 Rock name and minerals composition,
5. Sampling
6.2.7 Significant heterogeneities in appearance,
5.1 Stone specimens for petrographic examination are best
6.2.8 General physical condition of the specimen (for
obtained under guidance of a geologist familiar with the
example, freshness, weathering, alteration),
requirements of this standard. Information on the exact loca-
6.2.9 Presence and relative abundance of discontinuities
tion from which the specimen was taken and other pertinent
(for example, rock cleavage, foliation, bedding, layering,
data should be recorded or submitted with the specimen. The
fissures, fractures, vugs, stylolites, and fossils), and
amount of material actually studied in the petrographic exami-
6.2.10 Presence and relative abundance of constituents
nation will be determined by the nature of the examination to
known to be chemically or physically unstable.
be made and the nature of the material to be examined, as
discussed below. It is preferable that the specimens be selected
7. Report
and prepared by the person performing the petrographic
7.1 State purpose of the examination.
examination.
7.2 Summarize the essential data needed to identify the
5.2 Specimen(s) provided for examination with unknown
specimen as to source and proposed use, and include a
origin:
description giving the essential data on characteristics,
5.2.1 Often. specimens are submitted for petrographic
composition, and properties of the material as revealed by the
analysis without information as to origin. In this case, report
examination.
that the origin of the specimen is unknown or at
...

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.
Designation: C1721 − 21a C1721 − 22
Standard Guide for
Petrographic Examination of Dimension Stone
This standard is issued under the fixed designation C1721; 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.
1. Scope
1.1 This guide outlines procedures for the petrographic examination of stone specimen material proposed for use as dimension
stone used in construction.
1.2 This guide outlines the extent to which petrographic techniques should be used, the selection of petrographic related properties
that should be looked for, and the manner in which such techniques may be employed in the examination of dimension stone.
1.3 The rock and mineral names given in Terminology C119 should be used, insofar as they are appropriate, in reports prepared
in accordance with this guide.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
1.6 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:
C97 Test Methods for Absorption and Bulk Specific Gravity of Dimension Stone
C99 Test Method for Modulus of Rupture of Dimension Stone
C119 Terminology Relating to Dimension Stone
C120 Test Methods for Flexure Testing of Structural and Roofing Slate
C121 Test Method for Water Absorption of Slate
C170 Test Method for Compressive Strength of Dimension Stone
C217 Test Methods for Weather Resistance of Slate
C241 Test Method for Abrasion Resistance of Stone Subjected to Foot Traffic
C406 Specification for Roofing Slate
C503 Specification for Marble Dimension Stone
C568 Specification for Limestone Dimension Stone
This guide is under the jurisdiction of ASTM Committee C18 on Dimension Stone and is the direct responsibility of Subcommittee C18.01 on Test Methods.
Current edition approved Oct. 1, 2021April 15, 2022. Published November 2021May 2022. Originally published as C1721-09. Last previous edition approved in 2021
as C1721-21.-21a. DOI: 10.1520/C1721-21A.10.1520/C1721-22.
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
C1721 − 22
C615 Specification for Granite Dimension Stone
C616 Specification for Quartz-Based Dimension Stone
C629 Specification for Slate Dimension Stone
C880 Test Method for Flexural Strength of Dimension Stone
C1353 Test Method for Abrasion Resistance of Dimension Stone Subjected to Foot Traffic Using a Rotary Platform Abraser
C1526 Specification for Serpentine Dimension Stone
C1527 Specification for Travertine Dimension Stone
C1528 Guide for Selection of Dimension Stone
C1799 Guide to Dimension Stone Test Specimen Sampling and Preparation
E883 Guide for Reflected–Light Photomicrography
3. Summary of Guide
3.1 The specific procedures employed in the petrographic examination of any specimen will depend to a large extent on the
purpose of the examination and the nature of the specimen. In most cases the examination will require the use of optical
microscopy. Complete petrographic examinations for particular purposes and to investigate particular problems may require
examination of selected constituents by means of additional procedures, such as X-ray diffraction (XRD) analysis for crystalline
structure and mineral identification, differential thermal analysis (DTA) for chemically and physically unstable minerals, infrared
spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), or other procedures. Although these
procedures are beyond the scope of this standard, these additional procedures may be more definitive than visual microscopic
methods in certain circumstances.
3.2 Identification of the minerals, composition, rock fabric, and structure of a specimen is a necessary step towards recognition
of the properties that may be expected to influence the behavior of the material in its intended use, but identification is not an end
in itself. The value of any petrographic examination will depend to a large extent on the representativeness of the specimens
examined, the completeness and accuracy of the information provided to the petrographer concerning the source and proposed use
of the material, and the petrographer’s ability to correlate these data with the findings of the examination.
3.3 This guide does not attempt to describe the techniques of petrographic work since it is assumed that the guide will be used
by persons who are qualified by education and experience to employ such techniques for the recognition of the characteristic
properties of rocks and minerals and to describe and classify the constituents of a specimen that may have an effect on performance.
For some cases, the petrographer will have had experience adequate to provide detailed interpretation of the petrographic results.
For many cases the interpretation will be made, in part, by engineers, familiar with the intended use of the dimension stone. In
other cases, interpretation of the findings may require input of others, such as a chemist, qualified to relate the observations to the
questions to be answered.
3.4 The petrographer should be familiar with the ASTM standards referenced in 2.1.
4. Significance and Use
4.1 Petrographic examinations are made for the following purposes:
4.1.1 Determine the physical and chemical characteristics (mineralogy, texture, and composition) of the stone specimen that may
be observed by petrographic methods and that have a bearing on the performance of the material in its intended use.
4.1.2 Describe and classify the minerals of the specimen.
4.1.3 Classify the stone both commercially and geologically based on Terminology C119, recognizing the differences in
nomenclature; and based on the following standards, as appropriate:
Specification C406
Specification C503
Specification C568
Specification C615
Specification C616
Specification C629
Specification C1526
Specification C1527
C1721 − 22
4.1.4 Determine the relative amounts of the minerals of the specimen and constituents that have a bearing on the performance of
the material in its intended use.
4.1.5 Compare characteristics of the stone with specimens from one or more sources, for which test data or performance records
are available.
4.2 The petrographer should be told in as much detail as necessary, the purposes and objectives of the examination, the kind of
information needed, and the extent of examination desired.
4.2.1 Pertinent background information, including results of prior testing, such as physical and mechanical testing, should be made
available. The petrographer’s advice and judgment should be sought regarding the extent of the examination. Available physical
and mechanical testing may include the following:
Test Methods C97
Test Method C99
Test Method C170
Test Method C880
Test Methods C120
Test Method C121
Test Method C241
Test Method C1353
Test Method C217
4.3 This guide may form the basis for establishing arrangements between a purchaser of consulting petrographic service and the
petrographer. In such a case, the purchaser and the consultant should together determine the kind, extent, and objectives of the
examination and analyses to be made, and should record their agreement in writing. The agreement may stipulate specific
determinations to be made, observations to be reported, funds to be obligated, or a combination of these or other conditions.
4.4 Petrographic examinations provide identification of type and varieties of minerals and structures present in the specimen.
However, as noted above, identification of all minerals and structures present in the specimen is not necessarily required.
4.5 The petrographic examination should establish whether the specimen contains chemically unstable minerals or volumetrically
unstable materials.
4.6 Petrographic examination should identify weathered or otherwise altered constituents or minerals and describe the extent of
that weathering or alteration. Where possible, describe potential aesthetic changes that may occur as a result of weathering.
NOTE 1—If the dimension stone will be exposed to freezing and thawing and may become wet or saturated in use, finely porous and highly weathered
or otherwise altered minerals should be identified because these materials will be especially susceptible to damage by freezing and thawing.
4.7 Petrographic examination should identify constituents or minerals and the extent to which they may lead to staining and color
change of the surface of the stone when the stone is exposed to the weather for exterior use.
4.8 Petrographic examination should identify and estimate proportions of constituents that may be susceptible to deterioration
from attack by deicing agents where proposed for use at grade level in freezing environments where deicing salts are anticipated
to be used.
4.9 Criteria are available for identifying minerals by their optical properties or by XRD. Criteria are available for identifying rocks
by their mineral composition and texture. Examination in both reflected and transmitted light may be necessary to provide data
for these identifications. X-ray microanalysis using energy-dispersive X-ray spectrometers with scanning electron microscopy
(SEM/EDX) or wavelength-dispersive X-ray spectrometers in electron microprobes (EMPA/WDX) may provide useful
information on the chemical composition of minerals and rocks.
C1721 − 22
4.10 The objectives for which this guide was prepared, will have been attained if those involved with the evaluation of the
specimen have reasonable assurance that the petrographic examination results, wherever and whenever obtained, may confidently
be compared.
5. Sampling
5.1 Stone specimens for petrographic examination are best obtained under guidance of a geologist familiar with the requirements
of this standard. Information on the exact location from which the specimen was taken and other pertinent data should be recorded
or submitted with the specimen. The amount of material actually studied in the petrographic examination will be determined by
the nature of the examination to be made and the nature of the material to be examined, as discussed below. It is preferable that
the specimens be selected and prepared by the person performing the petrographic examination.
5.2 Specimen(s) provided for examination with unknown origin:
5.2.1 Often. specimens are submitted for petrographic analysis without information as to origin. In this case, report that the origin
of the specimen is unknown or attempt to obtain information from the submitter as to country, quarry of origin, and geologic
formation.
5.3 Specimen(s) selected from materials submitted for petrographic analysis as well as for physical and mechanical testing:
5.3.1 It is desirable to examine specimens that have been previously tested for physical and mechanical properties, for comparison
with non-tested specimens. Petrographic analysis can sometimes explain anomalous physical and mechanical results as well as
features that may be of concern, based solely on visual examination.
5.4 Specimen(s) selected from operating quarry for petrographic analysis.
5.4.1 Investigate vertical and lateral variations in the composition, texture, and microstructure of the material comprising the
formation.
5.4.2 Examine specimen stone material produced that is representative of material to be used.
5.4.3 Identify visible features and characteristics and their variations to aid purchaser in selecting stone for use.
5.4.4 Provide description or sketch of quarry and proposed extraction location(s), and locations from which specimens for
petrographic study were taken.
NOTE 2—Refer to Guide C1799 for additional information on selecti
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