Geotechnical investigation and testing - Identification, description and classification of rock (ISO 14689:2017)

This document specifies the rules for the identification and description of rock material and mass
on the basis of mineralogical composition, genetic aspects, structure, grain size, discontinuities and
other parameters. It also provides rules for the description of other characteristics as well as for their
designation.
This document applies to the description of rock for geotechnics and engineering geology in civil
engineering. The description is carried out on cores and other samples of rock and on exposures of
rock masses.
Rock mass classification systems using one or more descriptive parameters to suggest likely rock mass
behaviour are beyond the scope of this document (see Bibliography).
NOTE Identification and classification of soil for engineering purposes are covered in ISO 14688-1 and
ISO 14688-2. Identification and description of materials intermediate between soil and rock are carried out using
the procedures in ISO 14688-1, ISO 14688-2 and this document, as appropriate.

Geotechnische Erkundung und Untersuchung - Benennung, Beschreibung und Klassifizierung von Fels - Teil 1: Benennung und Beschreibung (ISO 14689:2017)

Dieser Teil der ISO 14689 beinhaltet die Benennung und Beschreibung von Gestein und Gebirge auf der Grundlage der mineralogischen Zusammensetzung, genetischer Aspekte, der Korngröße, der Trennflächen und anderer Kenngrößen. Er enthält auch Regeln für die Beschreibung anderer Eigenschaften sowie deren Bezeichnung.
Dieser Teil der ISO 14689 gilt für die Beschreibung von Fels in der Geotechnik. Die Beschreibung erfolgt an Bohrkernen und anderen Gesteinsproben sowie am Gebirge.
Felsklassifizierungssysteme, die eine oder mehrere beschreibende Kenngrößen verwenden, um das voraussichtliche Felsverhalten anzuzeigen, liegen nicht im Anwendungsbereich dieses Teils der ISO 14689 (siehe Literaturhinweise).
Die Benennung, Beschreibung und Klassifizierung von Boden für bautechnische Zwecke werden in ISO 14688 1 und ISO 14688 2 behandelt. Identifizierung und Beschreibung von Werkstoffen zwischen dem Boden und dem Gestein werden wie angemessen mithilfe der Verfahren in ISO 14688 1, ISO 14688 2 und ISO 14689 1 ausgeführt.
Ein Leitfaden mit der Beschreibung und Klassifizierung von Felsen wird in Norbury (2015) angegeben.

Reconnaissance et essais géotechniques - Identification, description et classification des roches (ISO 14689:2017)

Ce document spécifie les règles pour l'identification et la description du matériau et du massif rocheux sur la base de la composition minéralogique, des aspects génétiques, de la structure, de la taille des grains, des discontinuités et d'autres paramètres. Il fournit également des règles pour la description d'autres caractéristiques aussi bien que pour leur désignation.
Ce document s'applique à la description des roches pour la géotechnique et la géologie appliquée dans le génie civil. La description est effectuée sur des carottes et d'autres échantillons de roche et sur des affleurements rocheux.
Les systèmes de classification des massifs rocheux utilisant un ou plusieurs paramètres descriptifs permettant d'apprécier le comportement du massif rocheux sont hors du domaine d'application de ce document (voir Bibliographie).
NOTE       L'identification et la classification des sols pour les projets d'ingénierie sont couvertes par l'ISO 14688‑1 et ISO 14688‑2. L'identification et la description des matériaux intermédiaires entre le sol et les roches sont effectuées suivant les procédures les plus adaptées parmi celles de ce présent document, de l'ISO 14688‑2 et de l'ISO 14689‑1.

Geotehnično preiskovanje in preskušanje - Prepoznavanje, opisovanje in razvrščanje kamnin (ISO 14689:2017)

Ta dokument določa pravila za prepoznavanje ter opisovanje kamninskega materiala in mase na podlagi mineraloške sestave, genetskih vidikov, strukture, velikosti zrn, nehomogenosti in drugih parametrov. Poleg tega podaja tudi pravila za opisovanje in označevanje drugih značilnosti.
Ta dokument se uporablja za opisovanje kamnin za geotehnično in inženirsko geologijo na področju gradbeništva. Opisovanje se izvaja na jedrih in drugih vzorcih kamnin ter izpostavljenih kamninskih masah.
Sistemi razvrščanja kamninskih mas z uporabo enega ali več opisnih parametrov, ki kažejo na verjetno delovanje kamninske mase, ne spadajo na področje uporabe tega dokumenta (glej bibliografijo).
OPOMBA: Prepoznavanje in razvrščanje zemljin, namenjenih za uporabo v gradbeništvu, sta zajeta v standardih ISO 14688-1 in
ISO 14688-2. Prepoznavanje in opisovanje vmesnih materialov med zemljinami in kamninami sta izvedena z ustreznimi postopki v standardih ISO 14688-1 in ISO 14688-2 ter temu dokumentu.

General Information

Status
Published
Public Enquiry End Date
09-Sep-2016
Publication Date
19-Mar-2018
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
21-Feb-2018
Due Date
28-Apr-2018
Completion Date
20-Mar-2018

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SIST EN ISO 14689:2018
01-april-2018
1DGRPHãþD
SIST EN ISO 14689-1:2004
*HRWHKQLþQRSUHLVNRYDQMHLQSUHVNXãDQMH3UHSR]QDYDQMHRSLVRYDQMHLQ
UD]YUãþDQMHNDPQLQ ,62

Geotechnical investigation and testing - Identification, description and classification of

rock (ISO 14689:2017)
Geotechnische Erkundung und Untersuchung - Benennung, Beschreibung und
Klassifizierung von Fels - Teil 1: Benennung und Beschreibung (ISO 14689:2017)

Reconnaissance et essais géotechniques - Identification, description et classification des

roches (ISO 14689:2017)
Ta slovenski standard je istoveten z: EN ISO 14689:2018
ICS:
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
SIST EN ISO 14689:2018 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 14689:2018
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SIST EN ISO 14689:2018
EN ISO 14689
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2018
EUROPÄISCHE NORM
ICS 93.020 Supersedes EN ISO 14689-1:2003
English Version
Geotechnical investigation and testing - Identification,
description and classification of rock (ISO 14689:2017)

Reconnaissance et essais géotechniques - Geotechnische Erkundung und Untersuchung -

Identification, description et classification des roches Benennung, Beschreibung und Klassifizierung von Fels

(ISO 14689:2017) - Teil 1: Benennung und Beschreibung (ISO
14689:2017)
This European Standard was approved by CEN on 20 November 2017.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14689:2018 E

worldwide for CEN national Members.
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SIST EN ISO 14689:2018
EN ISO 14689:2018 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 14689:2018
EN ISO 14689:2018 (E)
European foreword

This document (EN ISO 14689:2018) has been prepared by Technical Committee ISO/TC 182

“Geotechnics” in collaboration with Technical Committee CEN/TC 341 “Geotechnical Investigation and

Testing” the secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by August 2018, and conflicting national standards shall

be withdrawn at the latest by August 2018.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 14689-1:2003.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 14689:2017 has been approved by CEN as EN ISO 14689:2018 without any modification.

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SIST EN ISO 14689:2018
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SIST EN ISO 14689:2018
INTERNATIONAL ISO
STANDARD 14689
First edition
2017-12
Geotechnical investigation and
testing — Identification, description
and classification of rock
Reconnaissance et essais géotechniques — Identification, description
et classification des roches
Reference number
ISO 14689:2017(E)
ISO 2017
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1  Scope ................................................................................................................................................................................................................................. 1

2  Normative references ...................................................................................................................................................................................... 1

3  Terms and definitions ..................................................................................................................................................................................... 1

4  Identification and description of rocks ........................................................................................................................................ 3

4.1 General ........................................................................................................................................................................................................... 3

4.2 Rock identification ............................................................................................................................................................................... 3

4.3 Geological formation and age ..................................................................................................................................................... 4

5  Rock material description .......................................................................................................................................................................... 4

5.1 Colour .............................................................................................................................................................................................................. 4

5.2 Grain size ...................................................................................................................................................................................................... 5

5.3 Unconfined compressive strength.......................................................................................................................................... 5

5.4 Weathering and alteration effects .......................................................................................................................................... 6

5.5 Carbonate content ................................................................................................................................................................................ 7

5.6 Degradation of rock material ...................................................................................................................................................... 7

6  Rock mass description.................................................................................................................................................................................... 7

6.1 General ........................................................................................................................................................................................................... 7

6.2 Rock types ................................................................................................................................................................................................... 8

6.3 Structure and bedding ...................................................................................................................................................................... 8

6.4 Discontinuities ........................................................................................................................................................................................ 8

6.4.1 General...................................................................................................................................................................................... 8

6.4.2 Measurement of discontinuity orientation ............................................................................................... 9

6.4.3 Discontinuity spacing ...............................................................................................................................................10

6.4.4 Rock block shapes in three dimensions ....................................................................................................10

6.4.5 Persistence of discontinuities ............................................................................................................................11

6.4.6 Roughness ...........................................................................................................................................................................11

6.4.7 Aperture ...............................................................................................................................................................................12

6.4.8 Infilling ..................................................................................................................................................................................13

6.4.9 Seepage .................................................................................................................................................................................13

6.4.10 Joint sets ...............................................................................................................................................................................13

6.5 Weathering of the rock mass ...................................................................................................................................................13

7  Fracture indices in cores ...........................................................................................................................................................................14

8  Rock mass classification ............................................................................................................................................................................15

9  Reporting ...................................................................................................................................................................................................................16

Annex A (informative) Aid to identification of rocks on the basis of geological features

for engineering purposes .........................................................................................................................................................................17

Annex B (informative) Classification of weathering of rocks (material and mass) ..........................................18

Annex C (informative) Description of discontinuities in three dimensions .............................................................20

Bibliography .............................................................................................................................................................................................................................21

© ISO 2017 – All rights reserved iii
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SIST EN ISO 14689:2018
ISO 14689:2017(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

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 182, Geotechnics.

This first edition of ISO 14689 cancels and replaces ISO 14689-1:2003, which has been technically

revised.
iv © ISO 2017 – All rights reserved
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
Introduction

This document gives details of the procedures to be followed in the identification and description of

rocks which are to be used at all stages of ground investigation and geotechnical design. This comprises

the description of the rock material and the rock mass characteristics in terms of the bedding and

discontinuities.

The level of detail in a description will depend on the characteristics of the rock, the size and quality of

the rock exposure or sample, and the needs of the particular project. The person carrying out the field

identification and description should be suitably qualified, skilled and experienced to make a correct

and appropriate description and experienced in the geological materials involved in the investigation.

Practice in rock identification and description varies from country to country, in part reflecting

significant differences in geological conditions. In addition, the quality of samples available for

description varies due to the investigation methods employed, as methods of investigation have been

developed in response to the ground conditions present.
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SIST EN ISO 14689:2018
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SIST EN ISO 14689:2018
INTERNATIONAL STANDARD ISO 14689:2017(E)
Geotechnical investigation and testing — Identification,
description and classification of rock
1  Scope

This document specifies the rules for the identification and description of rock material and mass

on the basis of mineralogical composition, genetic aspects, structure, grain size, discontinuities and

other parameters. It also provides rules for the description of other characteristics as well as for their

designation.

This document applies to the description of rock for geotechnics and engineering geology in civil

engineering. The description is carried out on cores and other samples of rock and on exposures of

rock masses.

Rock mass classification systems using one or more descriptive parameters to suggest likely rock mass

behaviour are beyond the scope of this document (see Bibliography).

NOTE Identification and classification of soil for engineering purposes are covered in ISO 14688-1 and

ISO 14688-2. Identification and description of materials intermediate between soil and rock are carried out using

the procedures in ISO 14688-1, ISO 14688-2 and this document, as appropriate.
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 14688-1, Geotechnical investigation and testing — Identification and classification of soil — Part 1:

Identification and description

ISO 14688-2, Geotechnical investigation and testing — Identification and classification of soil — Part 2:

Principles for a classification
3  Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
discontinuity

break in the rock material (3.7) continuity that is open or can open under the stress increase or

reduction as a result of the engineering works
3.2
duricrust

cemented zone occurring in weathered rock (3.5) or soil formed by the mobilization and deposition of

minerals often due to pedogenic or evaporative processes
© ISO 2017 – All rights reserved 1
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
3.3
fabric

preferred orientation or spatial arrangement of the constituent grains, crystals and matrix in the

rock (3.5)

Note 1 to entry: In sedimentary rocks, fabric is the orientation (or lack of it) in space of the constituents of

the rock. The term is used in igneous and other crystalline rocks for the patterns produced by non-uniform

arrangements of constituents.
3.4
foliation

planar arrangements of constituents such as crystals in any type of rock (3.5), especially the parallel

structure (3.11) that results from flattening, segregation and other processes undergone by the grains

in a metamorphic rock

Note 1 to entry: The original planar structure can be disrupted by folding or faulting during tectonic processes.

3.5
rock

naturally occurring assemblage or aggregate of mineral grains, crystals or mineral based particles

compacted, cemented or otherwise bound together and which cannot be disaggregated by hand in water

Note 1 to entry: Rocks are generally of greater strength than soils.
3.6
rock mass

rock (3.5) comprising the intact material together with the discontinuities and weathering zones

3.7
rock material
intact rock (3.5) between the discontinuities
3.8
rock matrix

groundmass of a rock material (3.7) which contains larger crystals, mineral grains or rock (3.5) particles

3.9
rock type

natural aggregation of one or more minerals or rock (3.5) fragments defined by its petrological

composition, predominant grain size, structure (3.11), texture (3.12) and genetic origin

EXAMPLE Common examples are given in Table A.1.
3.10
solid core

core with at least one full diameter uninterrupted by natural discontinuities, but not necessarily a full

circumference, commonly measured along the core axis or other scan line
3.11
structure

pattern of bedding, folds, faults and discontinuities in rock masses (3.6), which subdivide the mass into

individual domains or rock (3.5) blocks
3.12
texture

size, shape and arrangement of the grains or crystals that constitute a rock (3.5)

2 © ISO 2017 – All rights reserved
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
3.13
volumetric joint count

number of discontinuities (joints) in 1 m volume of rock mass (3.6) where Jv = 1/S1 + 1/S2 + 1/S3

Note 1 to entry: S1, S2, S3 are spacings (in metres) of each of the discontinuity (3.1) sets at a location.

4  Identification and description of rocks
4.1  General

Rocks shall be identified, described and classified in accordance with this document. The identification

and description of soils and the classification of soils shall be carried out in accordance with ISO 14688-1

and ISO 14688-2, respectively.

Identification and description of rocks are sub-divided into the following actions: (i) identification

(naming) of the rock (4.2), (ii) description of the rock material (Clause 5) and (iii) description of the

characteristics of the rock mass (Clause 6).

Guidance on several aspects of the identification and description of rocks is given in ISRM Suggested

[7][8]
Methods which can be usefully followed.
4.2  Rock identification

The identification of rock types shall be based on the determination of the following:

a) genetic group:
— sedimentary: clastic, chemical, organic;
— metamorphic;
— igneous: plutonic, volcanic;
— duricrusts;
b) structure:
— bedded, foliated or massive (without discontinuities);
— isotropy or anisotropy of the rock;
c) grain size:

— descriptive terms (for various sizes) are given in Table A.1 in correlation to rock types;

d) mineralogical composition:
— quartz, feldspars and related silicate minerals;
— dark coloured minerals (e.g. biotite, amphibole, pyroxene);
— clay minerals;
— carbonate minerals (e.g. calcite and dolomite);
— oxide minerals (e.g. magnetite);
— siliceous amorphous material (e.g. glass);
— carbonaceous material (e.g. coal and graphite);
© ISO 2017 – All rights reserved 3
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
— salts [e.g. halite (rock salt), gypsum];
— swelling minerals (e.g. anhydrite and clay minerals);
— sulfide minerals (e.g. pyrite);
e) void content:
— primary voids (e.g. gas bubbles in volcanic rocks);
— secondary voids (e.g. dissolution voids).

NOTE Lithological identification of rocks is necessary to appreciate the geology of an area, to correlate

geological profiles seen in boreholes or to distinguish boulders from bedrock. It is also important when rock is

required for construction purposes. Engineering properties can only partially be inferred from the identification

of rock type.

The names of the more common rock types are given in Table A.1, which presents an aid to rock

identification for engineering purposes.

Rock names are given particular combinations of features and correct naming requires recognition of

the attributes listed. The rock shall be correctly identified within geological science.

Geological maps and other documents related to the project such as the desk study shall be used for the

designation of rocks.
4.3  Geological formation and age

The identification of the rock should include, where possible, the geological formation that includes

the rock and its age taking into account all available information. The geological formation is usually

recorded after the name of the rock, in parentheses with capital letters.

Knowledge of the geological formation can provide useful information about the rock and the

interpolation between the boreholes in order to place a rock stratigraphically and to understand the

general geology.

If any age determination is thought to be of importance, experts should be appointed to carry out the

determination using appropriate dating methodologies.
5  Rock material description
5.1  Colour

The colour of the rock material shall be described using the simple system given in Table 1 to limit the

subjectivity of the description. One term is selected as required from each column and combined as a

colour assessment. Colours additional to those given in Table 1 would not often be appropriate.

Examples of use are: yellow, light yellowish brown, reddish brown. If necessary, colour differences can

be emphasized separately by the use of terms such as spotted, dappled, mottled, streaked; for example,

light yellowish brown spotted with dark brown.

A colour chart provides a useful aid, particularly to improve the consistency between descriptions

by different persons and under different lighting conditions. The best lighting conditions are outside

or near a window in bright cloudy weather; care should be taken if logging indoors under fluorescent

lights which most often give a green hue to the light. Logging areas should be lit by “blue” or “daylight”

lighting such as CIE D65 (which represents noon daylight, 6 500 K) or CIE C (which represents average

northern daylight, 6 774 K).

If the colour chart has colour codes, such as for hue, value and chroma, then these codes should be

included in the description.
4 © ISO 2017 – All rights reserved
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
Table 1 — Terms for lightness, chroma and hue colour description
Lightness Chroma Hue
Tertiary descriptor Secondary descriptor Primary descriptor
Red
Pink
Reddish
Orange
Pinkish
Light Yellow
Orangish
Cream
Yellowish
— Brown
Brownish
Green
Greenish
Dark Blue
Bluish
White
Greyish
Grey
Black
5.2  Grain size

The grain size(s) of the rock should be described using the descriptive scheme given in Table A.1.

Grain size refers to the average dimension of the predominant crystals, minerals or rock fragments

comprising the rock. It is usually sufficient to estimate the size by eye, which may be aided by a hand

lens in the assessment of fine-grained or amorphous rocks, but separate descriptions of the grains or

crystals and the matrix may be appropriate.

The particle size, the degree of cementation and the mineralogical composition of the matrix shall

be determined. Mineralogical composition should be described using the terms given in Table A.1

(siliceous, carbonate, carbonaceous, etc.) but may be amplified with such standard geological terms as

ferruginous, argillaceous (containing clay minerals), quartzose and others.
5.3  Unconfined compressive strength

The unconfined compressive strength of rock material can be estimated according to Table 2.

Table 2 — Unconfined compressive strength
Unconfined
compressive
Term Identification by hand test
strength
MPa

Extremely weak Scratched by thumbnail, gravel size lumps can be crushed between 0,6 to 1

finger and thumb

Very weak Scratched by thumbnail, lumps can be broken by heavy hand pressure, 1 to 5

can be peeled easily by a pocket knife, crumbles under firm blows with
point of geological hammer

Weak Thin slabs, corners or edges can be broken off with hand pressure, can be 5 to 12,5

peeled by a pocket knife with difficulty, easily scratched by pocket knife,
shallow indentations made by firm blow with point of geological hammer

Moderately weak Thin slabs, corners or edges can be broken off with heavy hand pres- 12,5 to 25

sure, can be scratched with difficulty by pocket knife, hand-held speci-
men can be broken with single firm blow of geological hammer

Medium strong Cannot be scraped or peeled with a pocket knife, specimen on a solid 25 to 50

surface can be fractured with single firm blow of geological hammer
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SIST EN ISO 14689:2018
ISO 14689:2017(E)
Table 2 (continued)
Unconfined
compressive
Term Identification by hand test
strength
MPa
Strong Specimen requires more th
...

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