Document KGpG4r1bVqqpzVVVg5jwLon80
FILE NAME Talc TALC
DATE 1977 July
DOC TALC142
DOCUMENT DESCRIPTION National Bureau of Standards Special Publication - Workshop Proceedings - Misidentification of
Asbestos in Talc
e
coe
.
National Bureau of Standards Special Asbestos Definitions and Measurement 1977. Issued November 1978
Publication 506 Proceedings of
Methods held at NBS Gaithersburg
the
MD
Workshop on July 18-20
MISIDENTIFICATION OF ASBESTOS IN TALC
Jerome B. Krause Colorado School of Mines Research Institute
Golden Colorado 80401
and
William H. Ashton
Johnson & Johnson
Raritan New Jersey 08869
Abstract
diffraction XRD are widely used
microscopy and ray
can
microscopy
Both optical
associated with talc Optical
to detect minerals
but cannot always fully identify
determine the morphology of a paXrRtDicilse an excellent screening technique ore
the specific mineral Although associated with talc the method can
for the detection of minerals
interpretive errors and the i
misidentify minerals due to interferences
!
inability to determine morphology
elimination of these problems include include
Methods for reduction or
and ray diffraction combined
special techniques of sample preparation and electron
with microscopic examination examination both optical
Key Words
morphology
asbestos chlorite electron microscopy
oApmtpihciablolmeiscroscopy ray diffraction talc
fiber
Introduction
misidentification naturally occurring material The
There are many ways to analyze and study any the expertise and specific interest
.
conclusions
reached will
often vary widely depending on
status of asbestos it is also
of the investigator
That situation sums up the present
and it is becoming the status
are associated with asbestos
the status of minerals whicbhe naturally associated with talc
of other minerals which can
namely that asbestos is
methods of analysis can give the wrong answer
is not so much one of
Popular it certainly is not
That problem
of data and failure to
present when
but rather one of misinterpretation
for example
limitations of the methods background required
recognize the mineralogical
for asbestos
silicates
to certify mineral Unfortunately one
purity
main factor is that of view is
wahsebnestaonsalhyazsinngow shdeeevteloped variable definitions dependiTnhgeonmwehdiectahler tdheefipnoiitniton is most
mineralogical
industrial
medical
not the
or regulatory
active the
particles
are biologically mineralogical
industrial definition
concerned with whether or
flexibility and weavability the
definition is dependeanntd tuhpeonregulatory definition upon size and aspect ratio
upon crystallography
Greek and has always referred to a very
The word asbestos stems from ancient
has historically related to a mineral
fibrous industrial mineral product Since asbestos think a combined mineralogical and
exploited as an important industrial commodity1, we2 Other presentations during this
industrial definition should take precedence
Figures in brackets indicate the literature references at the end of this paper
339
2063105132
peta
52200 52200
covered the aspects of asbestos
workshop have amply amply
of of that subject
to
provide
comprehensive comprehensive
coverage of
basic principlesprinciples
analysis
"
abused
and and
some of the of asbestos has been
identification
terminology terminology and it is not our Our primary objective is to
to point out problemproblem areas
intent
review
where
Analysis Methods and Misidentification of Asbestos
which which have been applied to
the various analytical analytical methods
asbestos as being
It is useful toto categorize
which lead to misidentifyingmisidentifying
determinative
determinative
talc to highlight inherent principles
comments on the three principle principle
present We offer the following general structure
properties chemical composition composition morphology
configuration Chemical Composition
and that
mineral
has
a
specific chemical
composition Unfortunately
It is well known that every
chemical formula
does not
each mineral
has
an ideal overlook
the
fundamental
point that chemical composition
into focus
will bring that point
many
investigators mineral
A simple example
identify a specific
and the
slab of marble a piece of chalk
and
A pearl an oyster shell a
obviously different materials
and calcite are
That is to say
carbonate
minerals aragonite
calcium
each will be identified as
the same substance where
,
i
yet
will identify them all as
chemical kannoawlsystehsat a pearl is not a piece of chalk i
everyone
For example
!
in certain phases of asbestos analysis
magnesium magnesium
The same situation exists
sepiolite
chlorite
and talc are all
hydrous asbestos
in
chrysotile
silicates
antigorite lizardite
is certainly not chrysotile
pipe sepiolite could lead to that misidentification
But a Meerschaum chemical analysis alone could
spite of the fact that
identify a mineral mineral nor do those sophisticated
Accordingly chemistry alone does cnhoemtical principles such as
instrumental methods which are based on
Wet Chemical Analysis
Classical gravimetric volumetric Instrumental atomic absorption flame emission
Microprobe electron and fon
Emission Spectrograph Mass Spectrograph
Ray Fluorescence
Morphology
of the key characteristics in the
the
shape
of a mineral
particle
is
one
the
sole
determinant
of
a
specific
Although of a mineral shape alone cannot be
mineral classes whose particles
identification
There are hosts
of
minerals in different of all
classes
of minerals
and the
mineral species shape
They exist across the
limit ourselves to minerals which occur
have the same
are beyond comprehension
Even if we
there are up to
100
There have
possibilities
in the true
fibrous state we would estimate
misidentified as chrysotile in talc
nonasbestos particles have been
been instances where
because shape alone alone was the index used
Methods based on morphology include
.
Optical Microscopy
2063153 Automated Image Analyzers
Electron Microscopy SEM and TEM
340
FOJOOindf FOJOOinFdOJOOfindf
:
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Structure
of atoms in the crystal lattice of a mineral does not necessarily
The configuration
at the molecular level does not always
determine a mineral species
The atomic arrangement
form
That is to say that methods based on
carry through to the external visible physical
molecular structure can misidentify a mineral
For
example chrysotile asbestos is
structure arrangement but it
classified with the sheet silicates because of its crystal
certainly does not occur in flat sheets like the micas or its sibling antigorite
Methods of identification which relate to molecular structure are
Infrared Spectroscopy
Differential Thermal Analysis
ray Diffraction
Electron Diffraction
In general then no single property defines a mineral depends on one property can identify a specific mineral
Conversely methods which depend on a single factor or
.
can give misidentifications
and no single characteristic
method which
.
of a mineral
Two Popular Methods
t
z
Optical
microscopy
and
diffraction methods require some additional
ray received
widespread
attention
by
industry
and
primarily because they have
laboratories as possible monitoring techniques
discussion
government
'
Although both highly reliable in
these methods are fundamental to the science
the hands of experts complications arise when
of mineralogy and are shortcuts are taken in
the professional procedures
Optical Microscopy
crystallographer When an experienced optical mineralogist orremarkablycrystaalclocgurarphaerteidceonnticfliuessioan miTnherealrewaistohn
a petrographic microscope he can bcuotmesetvoeraal specific properties are determined such as
for high accuracy is that not one refractive indices extinction angle
birefringence
and optical
orientation
Specific
training and wide mineralogical background are required to get the right answer
methods in federal regulatory proposals relating to
In contrast current optical
in the first place The analyst then merely
asbestos presume that asbestos is present for shape
Consequently those methods which depend
of asbestos
observes the mineral particle solely on aspect ratio give misidentification
They misidentify the presence it as an asbesti-
by such simple oversiigshtsnotas nleocoeksisnagry attoa epllaabtoerlaette ononedtghee anodthceorunsthionrgtcomings of those industrial talcs 3
mfeotrmhodpsaritniclvieew Iotf the recent NBS report on the analysis of 80
in a
evaluating that methodology The same shortcomings were also recently corroborated
study conducted by Harvard University and NIOSH 4
a few rare cases where abnormal crystal habit can be misleading
and
However there
subtly can lead
are to a
misidentification Optical microscopy is most vulnerable to this
talc normally occurs as micaceous plates but
type of misidentification For example
careful to avoid misidentifying the
rare
acicular
talc
does
exist
and
one must be very
XRD examination of an industrial
acicular
as asbestos As an example our
tremolite
rare occurrence has
identified
the
presence
of
significant amphibole
probably
talc sample
to thorough petrographic examination it was found
However when the material was subjected
and acicular tal^ and composite talc-
to be composed of free grains of columnar amphibole
conclusion could be reached by
amphibole The significance is that an erroneous
ratio and simple
misidentifying such a rare talc variety as asbestos if only aspect
optical microscopy were used
341
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2063105134
vw:
to
Thus simple optical microscopy can determine the morphology of a particle but if
used alone it cannot always fully identify the specific mineral observed
Ray Diffraction
Although ray diffraction XRD is a valuable technique it cannot determine the
physical
shape of a mineral
particle
and
for that reason it cannot determine whether or
it cannot distinguish between two mineral
not a sample is asbestos Furthermore
minerals and their
varieties in the same mineral class in cases such as the asbestos
nonasbestiform analogues It is surprising that such a basic shortcoming continues to be
overlooked by responsible investigators alleging to have identified asbestos by XRD
platy One result of the inability of powder XRD to differentiate between the asbestiform
and nonasbestiform varieties of a mineral is the potential error of prejudging an XRD
to be the asbestiform variety
For
example
preparing
calibration
.
dsettaencdtaredds pohfasemixtures of talc plus chrysotile could have the effect of causing a
serpentine peak in an unknown sample to be prejudged as mitnheeraalsbcheryssotilte icfhroyrsomtilevawirliletgyivei.teh.e
chrysotile A mixture of talc spiked with the serpentine
mineral
same XRD pattern as a mixture of talc spiked with the very common
serpentine
serpentine peak cannot be
antigorite
It should be obvious that an unknown talc showing a chrysotile asbestos under
such
circumstances
prejudged or branded as containing
authors who have overlooked that
Unfortunately the literature has articles by responsible
error in logic 5,6,7
For research purposes only single crystal XRD can provide information as to whether or not the specimen could be asbestos However due to the difficulty of handling minute specimens single crystal XRD is inadequate for particles smaller than about 20 ^ 5 ...m and of course is also inadequate for routine monitoring procedures
Amphiboles
Each of the five amphibole minerals anthophyllite cummingtonite riebeckite tremolite and actinolite has an asbestiform variety namely anthophyllite asbestos amosite crocidolite tremolite asbestos and actinolite asbestos respectively Tremolite asbestos is quite rare and actinolite asbestos is so rare that a recent NIOSH project to prepare reference standard minerals has been unable to locate a source of pure actinolite asbestos 8
The amphiboles named from the Greek amphibolos meaning ambiguous are characterized by similar crystal structure and wide variation in chemical composition and
appearance All amphiboles have XRD patterns which are similar and are characterized by having their 110 or 210 diffraction peaks occur within 0.2A of each other Table , Figure ) Reliable identification of individual amphibole species is difficult in the absence of confirming composition data
Examination of Table 1 and Figure 1 illustrates that attempted identification of a specific amphibole on the basis of daio or 210 has good potential for being in error For example selection of Joint Committee on Powder Diffraction Standards JCPDS card 13-437 as being definitive of tremolite presents serious problems Twenty additional JCPDS amphiboles have their 110 or 210 peaks within 0.1 of this tremolite 110 peak at 10.56 Identification of an amphibole as tremolite on the basis of a peak at 10.56 is obviously an identification with very low reliability In other words a peak at that location is not necessarily the mineral tremolite since it could be one of 29
other minerals
342
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Table 1.
JCPDS card #
23-118
10-456 20-734 20-378 14-633 21-149 19-467 20-982 23-665 23-664 23-667 23-663
9-434 13-499 20-656 20-470 23-666 20-469 23-1405 23-1406 20-1310
10-428 23-603 10-431 19-1061 20-481 20-1390 23-302 19-1063 13-437
17-478 23-495
9-330 17-750 20-386 22-531 16-401 17-725 17-745 20-376 17-726 20-484
13-506 23-679
9-455 20-453 11-253 23-310 13-401
or
peak position and
Amphibole JCPDS Card No's 110
210
relative intensity
ga
A
8.58
8.55
8.53
8.52
8.51
8.51
8.50
8.50
8.48
8.47
8.47
8.46 8.45
8.45
8.45
8.44
1
8.44
8.43
8.43
8.43
8.43
8.42
8.42 8.41
8.40
8.40
8.40 8.40
8.39
8.38
8.38
8.38
8.37
8.36
8.35
8.35
8.33
8.33
8.33
8.31
8.30
8.29
8.27
8.27
8.26
8.26
8.23
8.20
8.11
Cu
10.31 10.35 10.37 10.38 10.39 10.39 10.41 10.41 10.43
10.44
10.44 10.46 10.47 10.47 10.47 10.48 10.48 10.49 10.49 10.49
10.49 10.51 10.51 10.52 10.53 10.53 10.53 10.53 10.54 10.56 10.56
10.56 10.57 10.58 10.59 10.59 10.62 10.62 10.62 10.65 10.66 10.67
10.70 10.70 10.71 10.71 10.75 10.79 10.91
Name
prieskaite richterite
mboziite dashkesanite arfvedsonite hornblende
ferropargasite syn richterite syn
richterite calcian syn edenite sodian syn richterite calcian syn eckermanite calcian syn hornblende
magnesioriebeckite
magnesioriebeckite magnesioriebeckite crossite
tremolite sodian syn
hastingsite
edenite
paragasite
tremolite syn richterite fluor syn tirodite edenite fluor syn riebeckite hornblende
winchite cummingtonite mangoan richterite tremolite kaersutite eckermanite tremolite fluor syn richterite ferrian eckermanite syn
joesmithite anthophyllite magnesian syn grunerite grunerite
crossite
cummingtonitcum inegtonite
richterite
gedrite glaucophane
anthophyllianthtophyel ite
glaucophane ferrogedrite richterite ferrian holmquistite
a 110 or 210
Maximum A2e =
Table 1 illustrates
amphiboles showing
210 or 110
,
10.91 - 10.31 = 0.6
the very close proximity proximity of the inability to identify identify a
the 210 or 110 specific amphibole
XRD peak of all
on the basis of
2063156
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90 80
701
889880
889880 889880
889880
RIEBECKITE 20-656 19-1061 13-499 19-1061
TRENOSITE
i
ANTHOPHYLLITE
889880
8 98 0
8882899
888288982899
8882899
rT
t
ee
rt_\
wat
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a
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t
rp
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16-401 9-455
in
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8 8289
8 8289
8
INTENSITY
INTESITY
INTENSITY 100,
30 RELATIVE
RELATIVE
\
=
f
L
\
a
Lf.
\
Bh ee eee
on tose a
i
oo
\
fi \ aa Bt
f
ae ae
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ra
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RELATIVE tr
]
401
Bn a Teor Fy
Te. 2wlaeen ey
ee 30
SE
oe
20
See
10-
10-
100 |
| ee | |
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90 ama Ne ae ee 70 |
hai a
ee a
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70 mma nara rr Te
he
ee ;
a
ae
ee oa Sim ae a 7
|
a
a
oe a
et
||
10.6 o1 e 0.4 10.3
10.4
10.5
10.7
10.8
10.9
DEGREES 28 Cuk-
Figure 1.
Amphibole d
or d
- peak positions 20 for Cuk ) and relative intensity
110
210
An additional problem further affecting the reliability of identification by XRD is
the effect of shift in peak position caused by slight mispositioning of the sample surface
in the instrument For example a 100
mispositioning of the specimen surface will
...^m result in a shift of approximately 0.6-0.7 in spacing at low 28 angles 9 A slight
shift in the position of the peak from a different amphibole or mispositioning of the
sample surface for example could go unnoticed resulting in misidentification of an
amphibole that is not even present
2063105 37 In order to conclusively identify an amphibole by XRD it is necessary to have an
essentially complete diffraction pattern In order to obtain such an XRD pattern the sample must have a relatively high amphibole content and the pattern must be acquired with a consuming slow scan Acquisition and interpretation of such patterns is timeconsuming and discourages proper application of the full procedure especially for routine monitoring where large numbers of samples require analysis Shortened procedures such as single peak identification of amphiboles provide good opportunity for misidentification The shortened procedure of single peak identification was apparently used in a 1972 paper 7 where our examination of some of the same samples disagreed with
identifications of serpentine actinolite anthophyllite and anhydrite
344
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Serpentine
respectively minerals found associated with talcs
Chlorite is one of the most common accessory
to amphiboles in that they exhibit a
The chlorite group of minerals are somewhat anaalllogohuasve a similar crystal structure The
wide variation in chemical composition and
characteristic and occur
diagnostic chlorite basal
XRD
peaks
001
002
and
004
are
for
the
amphiboles
specific
at about 14A 7^ and 3.5^ respectively
As in the case
XRD is difficult
The XRD problem with
identification
of
a
particular
chlorite
species by
order
basal
peak
overlaps
the chlorite
002
talcs is that the serpentine first order basal peak overlaps the chlorite 004
chloritic
peak
and
the
corresponding
serpentine
second
and serpentine second order peaks are separate
peak Generally however the chlorite 004
of both phases when present in
enough
to
allow unambiguous
determination of the presence
2 and 3
and
Figures
2
3
and
4 are
adequate amounts to give definable peaks Tabolfes the 004 basal peak for chlorites and
compilations of JCPDS data for the positions
002 004 or 0012 basal peak for serpentines
Table 2.
Chlorite JCPDS relative
Card No's 004 peak positions and
intensity
JCPDS card #
10-183 20-671 16-351 12-185
7-160 19-749
7-77 16-362 19-751 22-712
7-165 7-78 7-171 12-242 7-76 13-29
7-166
12-243 21-1227
3-67
JA
3.60 3.60 3.59 3.57 3.58 3.56 3.558
3.55 3.55 3.55 3.545
3.541 3.541 3.54 3.537 3.53 3.523 3.52
3.52 3.49
Cu
24.73
24.73"
-
24.80 24.94 24.87
25.01
25.03 25.08 25.08 25.08 25.12 25.15 25.15 25.16
25.18 25.23 25.28 25.30 25.30 25.52
I
100 90 70 85 60 80 50 80 65 45 60 60 80 100 50 80 50 92 100 100
Name
penninite
k^/mmererite chlorite lb kotschubeite
kotschubeite clinochlore sheridanite chlorite la sudoite nimite grochauite thuringite diabantite
leuchtenbergite
ripidolite thuringite daphnite aphrosiderite
thuringite
thuringite
a
115
004 Table 2 ilustrates illustrates variation in position of the chlorited
XRD peak
Table
2
should
be
compared
with
Table
3
to
see
that
the
chlorite and
Identification
serpentine
XRD
peaks
overlap
and
interfere
with
each other of chlorite
is
extremely
and quantification of serpentine in the presence
difficult at best
345
20631538
bre brerr y brey ry usef oedu tid ump52d00
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|
|
30
8 828 98
882898
INTENSITY
INTENSITY
INTENSITY
RELATIVE 88828898
RELATIVE 88828898
RELATIVE
RELATIVE 2 <
RELATIVE
346
346
100
100
.
80
70
60
50
40
30
20
CHLORITE
16-362 16-362
a
-_
_.
_
-
iT
l
24.7
24.8
24.9
25.0
25.1
25.2
DEGREES 28 CuK
Figure 2.
Chlorite
- peak positions and relative intensity The data of Table 2 are presented in graphical form
004 004 showing the variation in position of the
XRD peaks for different chlorites Selection of JCPDS card
16-362 as diagnostic for chlorite can obviously result in misidentification
6-- IS01E907
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Table 3
Kaolinite Halloysite and Dickite JCPDS Card Nos
Serpentine peak position
miller
index
hkl
and
relative
intensity
JCPDS Card #
18-779
9-444 21-543
7-417 11-386 21-963 12-583 13-4
7-339
11-388
7-315 9-493
6-221 14-164 12-447
^
100
3.67 3.66 3.65 3.63 3.62 3.61 3.56
3.56 3.55 3.55 3.52 3.52
3.58 3.579 3.56
Cu
24.25 24.32 24.39 24.52 24.59 24.66
25.01 25.01 25.08 25.08 25.30 25.30
24.87 24.88 25.01
80 100
70 300
60 80 80 70 100 100 100 100
hkl
002
0012
004 102 002 002 0012 0012 002
0012
002 004
100+
002
80 2 ( 002
50
002
9-453 3.63 24.52 90
002
Serpentines lizardite 1M antigorite 60 chrysotile 2M antigorite 6M lizardite 10 aluminian antigorite 6M antigorite 60 aluminian
antigorite 60 aluminian
berthierine antigorite 60 syn berthierine amesite
Kaolinites kaolinite 1Md kaolinite IT kaolinite 11
Halloysite halloysite dehydrated
Dickite
10-446
3.58
24.87
100+
004
Chlorite 2e Range 24.73 - 25.52
dickite 2M1
of XRD peaks of serpentine kaolinite Table 3 illustrates variation in position of these minerals interfere with each
and dickite The XRD patterns
hotahlelroyasnidtewith chlorite see Table 2
347
206310540
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memes SERPENTINE 4002 0012 KSSSSSI KAOLINITE 4002 MER HALLOYSITE 40021
DICKITE 004
INTENSITY
INTENSITY RELATIVE
DEGREES 28 KK
variation positions positons position position Figure 3.
positions
and relative intensities The data of Table 3 are presented in graphical form to illustrate the
and interferring overlap of XRD peaks of serpentine kaolinite halloysite and dickite
IVISOIE907
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8280i
980
89
0
wen :
=== CHLOR0I0T4E _ SERPENTINE 1002 10012
... K... AOLIN...ITE d1002
coment HALLOYSITE jo02
=== DICKITE 004
_-
eee
4a
STITT
TT
IT.
=
an
CHLORITE
I i
i 16-362 I
TTT ee
TT
-
.
-
-
INTESIY I
349
98089808980
RELATIVE 980 980 980
40+ 40
ISO1E907
TCANTIGORITE 21-985
we
ee
.
rn
ay
-
~~
x
eS |
=
| ae
x
neunbenrnn |Ratan
ed
a A
230
231
252
25.325.3
25.425.4
Figure 4
Peak positions and relative intensities The data of Tables 2 and 3 are presented combined illustrating
the problems of XRD identification when chlorite and serpentine and possibly kaolinite halloysite or
dickite are also present
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in Tables 2 and 3 and Figures 2 3 and 4 Three essential features are demonstrated
variation in the position in
show considerable
1.05 for serpentines
1 The diagnostic peaks
for chlorites and
which they occur 0.79
and interfere with each other
2 The chlorites and serpentines serpentines overlap
minerals kaolinite halloysite and dickite Basal peaks of the clay the chlorite and serpentine peaks and will
3
overlap the positions of
interfere when present
is increased by the fact
of the serpentine interference
whereas serpentine
The significance
mineral associated with talcs
that chlorite is a very common accessory
is much less commonly associated .
investigators have performed
of
the
serpentine problem
numerous
chloritic talcs
It is obvious
In spite
quantification of serpentine in
by overlooking the
XRD identification and misidentified asbestos as being present
was serpentine
tsoeruspethnattithneye ihnatveerference and by misconcluding that a chlorite peak
Other Methods
Infrared Spectroscopy
IR
vibrational and bending
infrared
absorption
spectrum
of a material
results from
For example
Si stretching
The
within the structure
As a result IR spectra
frequencies of varioussimialtaormicIR bpoenadkss for all silicate minerals
in a mixture and the
frequencies produce
useful
for
identifying the minerals
present
detected mineral
is the
are not particularly
of determining whether or not a
method certainly is not capable
asbestiform variety
Differential Thermal Analysis DTA
structures due to thermal
or decomposition of mineral crystal
that DTA can identify
The rearrangement
and reproducible reaction
It follows
of determining morphology
heating isminaercahlasraicnteraismtiixcture but the method is not capabolfe a serpentine mineral could
specific
DTA data which might point to the presence the mineral could well be a
Therefore any
asbestos in a talc when
misidenfying chrysotile
the same DTA pattern
lead to
normally occurring platy antigorite antigorite having
206310543 sepiolite Electron Microscopy
of asbestos have been amply covered
identification
that subject
Electron microscopic techniques of
We do not intend to cover
in other presentations duoruitngsomtehiasreawsorwkhsehroepasbestos can be misidentified
again but rather to point
microscopy is in itself inadequate
The high magnification attainable with electron chrysotile is often identified by the
mineral identity For example
diffraction spots But the clay
as the sole indheoxlloofw central core and streaked electron
a similar electron
presence of a
mineral halloysite
also
crystallizes
in
that
form and will produce
chemical composition halloysite
Therefore in the absence of exact
to avoid misidentifying misidentifying
diffraction pattern
Similar care must be exercised
In
can be misidentified as asbestos
attapulgite and alpha
other
fibrous
clay
minerals as asbestos e.g. be mistaken to be asbestos
especially when some talcs have of a chrysotile particle
apdardtiitciloens wthailcch rroilblbounps icnatno spiral tubes giving the appearance
mineral particle
Selected area electron diffraction is routinetlhye uesleedcttroon iddeinftfirfayctiaon pattern in the
as amphibole Many investigators simply obserpvaettern geometry whether or not the particle
and decide on the basis of general
since numerous other minerals can
microscope
is an amphibole
This can lead to misidentification amphibole pattern
geometry
10,11
Careful
diffraction patterns with
in order to identify the type
is required
give electron
diffraction pattern
measurement of an electron
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of mineral which produced the pattern Chemical composition is further required in order to have a chance at identifying the particular species when the mineral is a member of a
complex group such as the amphiboles Otherwise misidentification will result
Cosmetic Talc Free from Asbestos
In the United States we have a regulating association known as the Cosmetic Toiletry and Fragrance Association In certifying the purity of the talcs which they use they are aware that no single method can identify asbestos and their most recent specification for cosmetic talc 12 combines two methods XRD and optical microscopy for
monitoring their types of talc
The rationale is that a talc is first examined by XRD and if
amount of amphibole is indicated then the test proceeds into optical dispersion staining technique to determine whether or not the asbestiform particles in the amphibole group
even the
microscopy
material
smallest using a
contains
Summary
This paper has categorized the main methods which have been used for detection of asbestos in talcs The basic principles of the various methods were categorized to explain how asbestos has been and can be misidentified in talc Generally misidentifications arise by jumping to a conclusion from a single mineral characteristic when in fact many characteristics are required to fully identify a mineral species and its variety
Both optical microscopy and XRD required a more detailed review than other methods since they have received the most attention from a monitoring point of view
This review is presented with the hope that our guidelines will enable analysts to
avoid the misidentification of asbestos in talcs
References
1 Ampian S. C. Asbestos minerals and their nonasbestos analogs Mineral Fibers Session Electron Microscopy of Microfibers Symposium Penn State Univ August 1976
2 Thompson C. S. Discussion of the mineralogy of industrial talcs U.S. Bureaouf
Mines Information Circular 8639 Proceedings of the Symposium on Talc Washington D.C. May 8 1973
3 National Bureau of Standards Staff A report on the fiber content of eighty industrial talc samples obtained from and using the procedures of the Occupational Safety and Health Administration 51 pp 1977
4
Bowndy M. G. Gold K. Burgers W. A. and Dement J. M. Exposure to industrial talc in Vermont talc mines and mills AIHA Conference presentation May 1977
5 Rohl A. N. Langer A. M. Selikoff I. J. Tordini A. Klimentidis R. Bowes D. R. and Skinner D. L. Consumer talcums and powders mineral and chemical characterization Jour of Toxicology and Environmental Health 2 255-284 1976
6 Rohl A. N. and Langer A. M. Identification and quantification of asbestos in
talc Environmental Health Perspectives 9 95-109 1974
7 Snider D. W. Pfeiffer D. E. and Mancuso J. J. Asbestos form impurities in commercial talcum powders Compass of Sigma Gamma Epsilon 49 65-67 1972
8 Scholl R. and Drafts R. 1977 XRD characterization of asbestiform reference
minerals Symposium on Electron Microscopy and Ray Applications to Environmenta
and Occupational Health Analyses April 1977
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ht p:/ legacy.library.ucsf.edu/tid/ump52d0 /pdhf ttp://legacy.library.ucsf.edu/tid/ump52d00/pdf
9 Jenkins R. A review of ray diffraction procedures as related to the quantitative
analysis of air particulates Symposium on Electron Microscopy and Ray Applications
to Environmental and Occupational Health Analyses April 1977
10
Zoltai T. and Stout J. H. Comments on asbestiform relative to Reserve Mining Company taconite deposits Control Agency 89 pp 1976
and fibrous mineral fragments Report to Minnesota Pollution
11
Lee R. Electron optical identification of particulates Symposium on Electron Microscopy and Ray Applications to Environmental and Occupational Health Analyses
April 1977
12 CTFA Specification - COSMETIC TALC Issued 10/7/76 The Cosmetic Toiletry and Fragrance Association Inc.
Discussion
A. WILEY You said that instantaneous recognition of SAD patterns is difficult Could
you give some examples as to what kind of confusions could exist in this Can you confuse amphibole with serpentine or amphibole with talc or is that kind of a gross mistake
possible
.
J. KRAUSE Those kinds of mistakes probably would not generally happen if you are
looking at pyroxenes or olivine Electron diffraction is not one of my areas of real expertise but I think that you could possibly get feldspars that would give confusing
patterns depending upon their orientation in the microscope
L. MADSEN We are using all the methods that have
fication for asbestos materials and do not in any way
aspect ratios
been talked about today for identilimit ourselves to fiber length and
J. WAGMAN I would like to comment that it is possible by ray diffraction and
through a special technique to identify and measure the presence of asbestos fibers even when they are in the presence of their fibrous counterparts About two years ago this was demonstrated in a study which we supported at the Naval Research Laboratory in which samples were treated so that fibers were first aligned and then the ray diffraction intensities measured at two different orientations with respect to the ray beam and in
this way the intensity due to the fibrous counterparts could be subtracted from the
total diffraction intensities
KRAUSE You were putting the fibers in some specific preferred orientation in the
sample and then looking for those orientations by XRD
WAGMAN That is correct and this had the advantage corrections that is correcting for the fibrous material enhances the detectability for the fibers themselves
of not only making possible
present but also it greatly
KRAUSE Is this method being currently used
WAGMAN This is a method whose feasibility was demonstrated and there are two publica-
tions on this in the literature Actually our objective was to apply this method to
airborne samples which is a much more difficult application incidently I should think
than in the case of talc The problem here is a preparative problem in that an air sample
usually has a lot of organic material sticky material present which interferes with the
ability to orient the fibers This is a preparative problem which will have to be overcome
But
should think that in the case of talc samples you probably would not have that
problem
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K. HEINRICH the fibers
Would the talc plates interfere just as well with the orientation of
WAGMAN The orientation of the fibers is accomplished in an electric field and the
platy material does not preferentially orient itself
HEINRICH fibers
I mean just in the sense of a passive restraint to the movement of the
WAGMAN This of course would have to be tested experimentally
A. LANGER We heard today from a representative of one of the member organizations of the Cosmetic Fragrance and Toiletry Associations that of 3800 consumer talcs examined none contained chrysotile Today you presented some interesting information on
the identification of crocidolite in talc Have you seen crocidolite in many talcs you
have examined
KRAUSE No I have not seen it nor did I say that I have
LANGER It does not occur in consumer talcs or is it industrial
not see why the crocidolite issue was raised have you seen it
talc
I just do
KRAUSE Just because I have not seen it certainly does not mean that it could not
conceivably exist All I was trying to do was point out that choosing a specific
amphibole peak as being representative and definitive for giving a good identification of
a particular amphibole species has great potential for error There are many many other
minerals that could fall within that same two theta region
,
LANGER I would agree with you that even though talcs occur in nature and they have great mineralogical variability they are still bound by the physical and chemical laws involving silicate rock systems A mineral phase such as you described would not
occur normally
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