ISO 22444-1:2020

INTERNATIONAL ISO
STANDARD 22444-1
First edition
2020-10
Rare earth — Vocabulary —
Part 1:
Minerals, oxides and other compounds
Terres rares — Vocabulaire —
Partie 1: Minéraux, oxydes et autres composants
Reference number
ISO 22444-1:2020(E)
©
ISO 2020

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ISO 22444-1:2020(E)

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© ISO 2020
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Published in Switzerland
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ISO 22444-1:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Terms related to rare earth minerals and ore . 4
4.1 Rare earth minerals . 4
4.2 Rare earth ores and concentrate . 5
5 Terms related to rare earth oxides and other compounds . 6
5.1 General terms . 6
5.2 Rare earth compounds . 6
6 Terms related to the rare earth production process . 9
6.1 Production of rare earth concentrate . 9
6.2 Rare earth hydrometallurgy . 9
Annex A (informative) Characteristics of rare earth elements and individual rare earth oxides .10
Bibliography .13
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ISO 22444-1:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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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
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 298, Rare earth.
A list of all parts in the ISO 22444 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 22444-1:2020(E)

Introduction
Rare earth elements are widely used. Different business and industry sectors have various descriptions
for rare earth elements and their compounds and alloys. Therefore, it is of vital importance to unify the
terminology used in the rare earth industry.
About 250 minerals contain significant amounts of rare earth elements although there are only a
few that are economically exploited at this time. Various rare earth oxides and other compounds are
obtained from these rare earth minerals as they are processed through to intermediate products and
on to final products.
This document specifies terms for use by producers, consumers and traders in the field of rare earth
minerals, oxides and other compounds. This document will serve as a reference that will help to reduce
discrepancies or trade disputes caused by inconsistencies in terms used when dealing with rare earth
minerals, oxides and other compounds.
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INTERNATIONAL STANDARD ISO 22444-1:2020(E)
Rare earth — Vocabulary —
Part 1:
Minerals, oxides and other compounds
1 Scope
The document defines the terms for rare earth minerals, oxides and other compounds, as well as for
related production processes.
This document can be used as a reference to unify technical terms in rare earth production, application,
inspection, circulation, trading, scientific research and education.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
rare earth element
collective name for scandium (Sc), yttrium (Y) and the lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, Lu), which was approved by the International Union for Pure and Applied Chemistry
[1]
(IUPAC) in its 2005 Nomenclature of Inorganic Chemistry Recommendations
Note 1 to entry: Certain terms and corresponding abbreviated terms are common such as rare earth element
(REE or RE) and rare earth oxide (REO) (5.2.1).
Note 2 to entry: Rare earth elements are frequently referred to as being either light rare earth (LREE), medium
rare earth (MREE) or heavy rare earth (HREE), with LREE including the elements between lanthanum (La)
and neodymium (Nd), MREE including the elements between samarium (Sm) and gadolinium (Gd), and HREE
including the elements from terbium (Tb) to lutetium (Lu) as well as scandium (Sc) and yttrium (Y).
Note 3 to entry: Didymium is commonly used to express a mixture of the elements Pr and Nd.
Note 4 to entry: Characteristics of rare earth elements are described in Annex A.
3.2
rare earth mineral
mineral containing one or more rare earth elements (3.1)
Note 1 to entry: Rare earths can be present as a simple compound, incorporated in the lattice of another mineral,
or sorbed to another mineral, such as bastnaesite (4.1.1), monazite (4.1.2) or montmorillonite as in ionic clay
deposits.
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ISO 22444-1:2020(E)

3.3
rare earth ore
rare earth mineralization found in nature in various types of ore deposit
Note 1 to entry: Those deposit types that are now, or have previously been, commercially exploited include
Baiyun Obo ore (4.2.1), ion-adsorption rare earth ore (4.2.2), carbonatite/alkalic pipe (4.2.3), weathered carbonatite
(4.2.4) and beach sand (4.2.5).
3.4
rare earth deposit
area or volume of the earth’s crust where there is an accumulation of rare earth minerals (3.2), with or
without other valuable minerals, that is of economic interest
3.5
rare earth grade
mass fraction of rare earth oxide (REO) (5.2.1) in the deposit/concentrate or tailings
Note 1 to entry: The grade can be present as a percentage or as either kg/t or g/t. Statements of grade shall
clearly state if the data are given on a REE, RE or REO basis.
Note 2 to entry: When a rare earth metal mass is converted to oxide mass, all rare earth elements (REEs) (3.1)
should be taken as trivalent except for the following oxide forms: ceric oxide, CeO , praseodymium oxide, Pr O ,
2 6 11
and terbium oxide, Tb O .
4 7
3.6
rare earth mineral resource and mineral reserve
resources of ore or minerals containing rare earths, which can be mined legally and profitably under
existing conditions
Note 1 to entry: Indicated reserve is the estimate of ore computed from boreholes, outcrops and developmental
data, and is projected for a reasonable distance on geologic evidence.
3.7
rare earth content
total rare earth content
mass fraction of rare earths in the material
Note 1 to entry: For rare earth oxides (5.2.1) and other compounds, the fraction is generally provided as a
percentage of rare earth oxide, i.e. % REO or % TREO. For metals and alloys, the content is generally provided as
a percentage of rare earth metal, i.e. % REM or % TREM.
3.8
rare earth distribution
mass fraction of each individual rare earth in a material containing a mixture of rare earths compared
to the rare earth content (3.7) of the material
Note 1 to entry: The distribution is normally expressed as the percentage of rare earth metal, i.e. % RE or % REM
for metals and alloys, and percentage of rare earth oxide (5.2.1), i.e. % REO, for compounds and other materials.
3.9
average molar mass of mixed rare earth compounds
M
ratio of the total mass of all rare earth compounds to their total number of moles, as shown by the
formula:
N
m
m mm++…+m
∑ i
total i=1 12 N
M== =
m m m
n N m
i 1 2 N
total
++…+
∑
i=1
M M M M
i 1 2 N
where
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ISO 22444-1:2020(E)

m is the total mass of mixed rare earths, in g;
total
n is the total number of moles of mixed rare earths, in moles;
total
m is the mass of rare earth compound i, i = 1, 2, …, N, in g;
i
M is the molar mass of rare earth compound i, i = 1, 2, ., N. The basic unit of calculation is
i
1/x(RE B ), in g/mol.
x y
Note 1 to entry: M is given in g/mol.
EXAMPLE 1 The average molar mass of a mixed rare earth oxide (5.2.1) containing 40 % mass of lanthanum
oxide and 60 % of yttrium oxide is calculated as follows:
m = 40 units, m = 60 units, M = 325,81/2 = 162,90 g/mol, M = 225,81/2 = 112,90 g/mol
La2O3 Y2O3 La Y
40+60
M= =128,/7gmol
40 60
+
162,,9 112 9

EXAMPLE 2 The average molar mass of a mixed rare earth oxide (5.2.1) containing 25 % of praseodymium
oxide and 75 % of neodymium oxide is calculated as follows:
m = 25 units, m = 75 units, M = 1 021,44/6 = 170,24 g/mol, M = 336,48/2 = 168,24 g/mol
Pr6O11 Nd2O3 Pr Nd
25+75
M= =168,/7gmol
25 75
+
170,,2 168 2

EXAMPLE 3 The average molar mass of a mixed rare earth chloride (5.2.2) containing 40 % of lanthanum
chloride and 60 % of cerium chloride is calculated as follows:
m = 40 units, m = 60 units, M = 245,26 g/mol, M = 246,48 g/mol
LaCl3 CeCl3 LaCl3 CeCl3
40+60
M= =246,/0 g mol
40 60
+
245,,26 246 48

3.10
rare earth impurity
undesirable rare earth element (3.1), apart from the target rare earth component(s) in a rare earth product
3.11
non-rare earth impurity
undesirable non-rare earth component in a rare earth product
2-
EXAMPLE Fe, Al, Ca, SO .
4
3.12
rare earth purity
absolute rare earth purity
mass fraction of a specified rare earth element (3.1) or rare earth oxide (5.2.1) in a rare earth product
Note 1 to entry: It is expressed as a percentage and with the basis (REM or REO) stated.
Note 2 to entry: The content of target element in the oxide, metal or compound is expressed by purity when the
content is higher than 90 %.
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ISO 22444-1:2020(E)

3.13
relative rare earth purity
mass fraction of the specified rare earth element (3.1) or rare earth oxide (5.2.1) out of the rare earth
content (3.7)
Note 1 to entry: It is expressed as a percentage and with the basis (REM or REO) stated.
4 Terms related to rare earth minerals and ore
4.1 Rare earth minerals
4.1.1
bastnaesite
yellow, reddish brown, light green or brown carbonate-fluoride mineral, usually containing 65 % to
75 % rare earth oxide (5.2.1), with the formula of (Ce,La,Nd,Pr) CO F
3
Note 1 to entry: The family of carbonate-fluoride minerals includes bastnaesite-(Ce) with a formula of (Ce,La)
CO F, bastnaesite-(La) with a formula of (La,Ce)CO F, and bastnaesite-(Y) with a formula of (Y,Ce)CO F. Most of
3 3 3
the mineral is bastnaesite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals.
3
Note 2 to entry: The Mohs hardness of the mineral is 4 to 4,5, and the density is generally 4 700 kg/m to
3
5 100 kg/m .
Note 3 to entry: The mineral is soluble in HCl, H SO , HNO and H PO .
2 4 3 3 4
4.1.2
monazite
yellow-brown, brown, red and sometimes green mineral, usually containing 55 % to 70 % of rare earth
oxide (5.2.1), with the formula of (Ce,La,Nd,Pr,Th)PO
4
Note 1 to entry: The mineral is usually found in small free crystals, and the mineral composition is mostly light
rare earth. The presence of thorium can create radioactivity issues.
3
Note 2 to entry: The Mohs hardness of the mineral is 5,05 to 5,5, and the density is generally 4 900 kg/m to
3
5 500 kg/m .
Note 3 to entry: The mineral is soluble in H PO , H SO and HClO depending on composition and pre-treatment
3 4 2 4 4
processes.
4.1.3
xenotime
yellow, brown and sometimes yellowish green rare earth phosphate (5.2.9) mineral, typically containing
50 % to 65 % rare earth oxide (5.2.1), which is generally yttrium phosphate (YPO )
4
Note 1 to entry: Besides yttrium, the mineral often contains other heavy rare earth elements (3.1) such as
dysprosium, erbium, terbium and ytterbium. The presence of thorium can create radioactivity issues. The
mineral is a significant source of yttrium and heavy rare earth metals.
3 3
Note 2 to entry: The Mohs hardness of the mineral is 4 to 5 and the density is generally 4 400 kg/m to 5 100 kg/m .
4.1.4
fergusonite
typically yellow, tawny or black complex mineral, typically containing 43 % to 53 % rare earth oxide
(5.2.1), with the chemical formula of (Y,REE) NbO
4
Note 1 to entry: Usually, the main rare earth in the mineral is yttrium, but sometimes cerium, lanthanum and
neodymium can be substituted.
3
Note 2 to entry: The Mohs hardness of the mineral is 5,5 to 6,5 and the density is generally 4 900 kg/m to
3
5 800 kg/m .
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ISO 22444-1:2020(E)

Note 3 to entry: The mineral is partially dissolved in HCl and dissolved in H SO , H PO and HF depending on
2 4 3 4
composition and pre-treatment processes.
4.1.5
loparite
black, ash black or streak reddish brown mineral, typically containing 30 % to 40 % rare earth oxide
(5.2.1), with a general chemical formula of (Na,Ce,Ca,La,Sr)O (Ti,Nb)
3
3 3
Note 1 to entry: The Mohs hardness is 5,6 to 6,0 and the density is generally 4 600 kg/m to 4 900 kg/m .
Note 2 to entry: If the Nb O is greater than 25 %, it is called niobium-rich loparite.
2 3
Note 3 to entry: The mineral is generally not soluble in acids except for hydrofluoric acid.
4.2 Rare earth ores and concentrate
4.2.1
Baiyun Obo ore
mixed rare earth ore (3.3) containing rare earth elements (3.1) in bastnaesite (4.1.1) and monazite (4.1.2)
and iron as magnetite and hematite
Note 1 to entry: It is named after Baiyun Obo in Inner Mongolia where the ore is processed for the production of
rare earth concentrate (4.2.6) and iron concentrates.
4.2.2
ion-adsorption rare earth ore
clay minerals, such as montmorillonite, that have sorbed rare earth ions released by intense weathering
of primary rare earth minerals (3.2) through ion exchange mechanisms, also known as weathered crust
elution-deposited rare earth ore (3.3)
Note 1 to entry: The ore is a major source of heavy rare earths and is found in various parts of the world, generally
in the tropics.
4.2.3
carbonatite/alkalic pipe
rare earth deposits (3.4) hosted by carbonatite/alkalic pipes and overlying alkali volcanic deposits
Note 1 to entry: The rare earth mineralization is often in the form of bastnaesite (4.1.1) although monazite (4.1.2)
is also frequently encountered. Gangue minerals are usually carbonates.
EXAMPLE Mountain Pass in the USA, Kvanefjeld in Greenland.
4.2.4
weathered carbonatite
carbonatites having experienced intensive weathering and leaching processes that have, in many cases,
led to enrichment of the rare earths
EXAMPLE Mt. Weld deposit in Australia, the Tomtor deposit in Russia.
4.2.5
beach sand
rare earth minerals (3.2) that generally have high specific gravities and can be concentrated by the
action of flowing water in coastal or riverine heavy mineral deposits
Note 1 to entry: Su
...