1-International Asbestos Testing Laboratories, Inc. Mount Laurel, NJ
2-MVA Scientific Consultants, Inc. Duluth, GA
3-Minerals Technologies, Inc. Easton, PA
Special Thanks to Robert Shumate of IATL Inc. for TEM analysis performed
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This investigation is part of a currently informal study performed by active members of the
American Society for Testing Materials (ASTM). member interest is in characterization of erionite
specimens and site specific samples containing erionite that may lead to development of
standard test methods. Traditional environmental laboratory methods of analysis (XRD, SEM,
TEM, PLM) are used for characterization.
Erionite is a naturally occurring, fibrous zeolite mineral with properties and health effects similar
to asbestos. It usually is found in volcanic ash/tuffs that has been altered by weathering and
ground water. Erionite is classified as an IARC Class I carcinogen based on epidemiology studies
from exposure in the Cappadocia region of Turkey (IARC monographs 42:225-239, 1987).
Erionite is not currently regulated by the U.S. Environmental Protection Agency (EPA) in the same
manner as asbestos.
Cappadocia studies promoted increased awareness of exposure risk potential resulting from
gravel pit excavation and disturbance of rock formations/soils during engineering activites that
may contain zeolites. Identification of erionite occurrences and exposure risk has increased
since the 1970’s Cappadocia study.
The North Dakota Department of Health, in cooperation with EPA, is currently conducting
erionite exposure risk from Arikaree, Brule and Chadron geologic formations (Chalky Buttes,
Little Badlands and Killdeer Mountain areas) in Slope, Stark and Dunn counties of North Dakota.
Procurement of reliable zeolite specimens can be challenging due psuedomorphism, difficulty
in hand specimen identification without proper analytical confirmation, changes in mineral name
classification and nomenclature.
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Initial focus on comparative characterization of verified erionite and
other fibrous elongate zeolite specimens. Verified reference specimens
from Rome Oregon, Cappadocia Turkey and Durkee Oregon are in the
process of being characterized by ASTM members. A multi-analytical
approach for characterization and identification of erionite is
anticipated. Other fibrous/elongate zeolite and erionite specimens
procured from various sources have been analyzed previously and
reported on. Analytical methods commonly used in environmental and
mineral R&D laboratories are and have been used for this study:
1. X-Ray Powder Diffraction (XRD)-Accepted definitive structural Identification/verification
of zeolites.
2. Scanning Electron Microscopy (SEM) & Energy Dispersive X-Ray Analysis (EDX)Morphology & cation analysis.
3. Transmission Electron Microscopy (TEM) & EDX-Morphology and cation analysis. Focus on
4. Polarized Light Microscopy (PLM) & Central Stop Dispersion Staining (CSDS) using a
bench formulated High Dispersion (HD) 1.47 Refractive Index Liquid (RIL)-possible
screening technique for differentiation of erionite from other fibrous/elongate zeolites.
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Identification of Zeolites:
1. Complex, naturally occurring framework aluminosilicate minerals
(tectosilicate group). Characterized from other framework silicates, and
differentiated from each other by the presence and number of water
molecules.
2. The International Commission on New Minerals and Mineral Names
(CNMMN) recognized general zeolite formula:
(Ca,Na2,K2,Ba,Sr,Mg,Cs2,Li2)a[AlaSin-a02n] •xH2O.
3. There are 82 CNMMN recognized mineral species (13 compositional
series) and over 150 synthesized zeolites.
4. Identification of zeolite species can be challenging due to similarities in
physiochemical properties.
Specimen
XRD Validation
Karain, Cappadocia Turkey Erionite
Durkee OR Erionite
Rome OR Erionite
Chase Creek, Erionite
Beech Creek, Erionite-Ca
Mordenite, Goble Cty
Thomsonite, Sagasen
Natrolite , Lane Cty
Mesolite, Skookumchuck
Erionite/Qtz/Anor
Erionite
Erionite/chabazite/qtz/Anor
Offretite (sold as erionite)
Chabazite and Thomsonite
Mordenite
Natrolite
Natrolite
Mesolite
Karain, Cappadocia Turkey Erionite
Durkee Oregon Erionite
Rome Oregon Erionite
Chase Creek Offretite (sold as Erionite)
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ICDD card matches for Rome Oregon and Cappadocia
(Karain) Turkey erionite same (04-010-5070 & 000012-0275).
Peak
intensity/shape/symmetry
suggests high crystallinity. Suggests Rome & Karain
have similar chemistry. PLM examination consistent.
ICDD card match for Durkee Oregon slightly different
compared to Rome and Karain (no 000-012-0275).
Suggests different chemistry. Peaks suggest poor
cyrstallinity, possibly differences in structure
compared to Rome & Karain.
Accessory mineral XRD identification for Rome and
Karain same (quartz, chabazite, anorthite). Hand
specimen and PLM examination consistent.
Tem Image 40,000X
iATL
INTERNATIONAL
Client ID:
EDX Data
IATL Sample #:
ASBESTOS TESTING LABORATORIES
EDXA ID:
ASTM
Non-ACM Standard
Durkee Erionite
Plate #
Micrograph Plate # (if applicable):
Chemical Composition
Cam Length Exp. Time
0.3
60
TEM Image 12,000X
EDX Data
iATL
Client ID:
ASTM
INTERNATIONAL
IATL Sample #:
ASBESTOS TESTING LABORATORIES
EDXA ID:
Non-ACM Standard
Rome Erionite
Plate #
Micrograph Plate # (if applicable):
Chemical Composition
Cam Length
0.3
Exp. Time
60
TEM Image 5,000X
iATL
INTERNATIONAL
EDX Data
Client ID:
IATL Sample #:
ASBESTOS TESTING LABORATORIES
EDXA ID:
ASTM
Non-ACM Standard
Cappadocia Erionite
Plate #
Micrograph Plate # (if applicable):
Chemical Composition
Cam Length Exp. Time
0.3
60
iATL
Client ID:
ASTM
INTERNATIONAL
TEM Image 8,000X
IATL Sample #:
ASBESTOS TESTING LABORATORIES
EDX Data
EDXA ID:
Non-ACM Standard
Chase Creek Offretite (sold as Erionite)
Plate #
Cam Length
0.3
Micrograph Plate # (if applicable):
Exp. Time
60
Chemical Composition
iATL
Client ID:
ASTM
INTERNATIONAL
IATL Sample #:
ASBESTOS TESTING LABORATORIES
EDXA ID:
Non-ACM Standard
Chase Creek Erionite
Plate #
Micrograph Plate # (if applicable):
Chemical Composition
Compositional Variation on Ca, Mg, K, Na along fiber lengths. One end
K+Na>Mg+Ca, other end reversed. Suggests erionite intergrowths
Cam Length
0.3
Exp. Time
60
Pattern not indexed at date of
presentation, further work to be
performed in future. Limited
SAED suggests hexagonal
pattern, diffuse (not sharp)
spots expected for erionite.
Specimen
Si:Al
Si:K
Al:Ca
K:Ca
Al:K
Chase Creek Offretite
3:1
6-7:1
1.5-2:1
0.7-1:1
2-2.5:1
Karain Erionite
3.5-4:1
4-5.5:1
2.8-3.7:1
2.2-3:1
1.1-1.5:1
Durkee Erionite
3.5-4:1
4-5.7:1
2.7-3.8:1
1.8-2.3:1
1.3-1.7:1
Rome Erionite
3.5-4:1
4-5.5:1
3.3-4.5:1
1.8-3.5:1
1.1-1.6:1
TEM Observations
1-Rome, Karain and Durkee Erionite specimens have similar morphology by TEM, similar to Offretite (Chase
Creek).
2-Chase Creek specimen EDX analysis indicates distinctly different chemical composition at ends of fibers. This
suggests offretite with intergrowths of erionite (not detectable by XRD). Na+K>Mg+Ca domains suggest
erionite, Mg+Ca>Na+K domains suggest offretite.
3- Erionite specimens examined have similar EDX spectra, quantitative elemental analysis indicates variation of
cation content (expected) for six fibers analyzed for each specimen.
4-Comparison of elemental ratios (table above) suggests that Si:Al, Si:K and Al:K may be useful
for differentiating erionite from other fibrous zeolites on the basis of the limited data
acquired at time of this presentation. Further work on other erionite and
fibrous zeolite specimens required.
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Erionite Identification Screen by PLM-Process of Elimination:
1. CSDS is an optical microscopy contrast enhancement technique for measuring RI that is
more sensitive than the Becke-line method. It is an established asbestos minerals
identification technique using 1.550 (chrysotile), 1.605 (actinolite,tremolite, anthophyllite)
and 1.680 (amosite, crocidolite). Magenta blue CSD of a particle indicates a “ RI match” with
a liquid, blue CSDS indicates the RI of the particle is less than the liquid, and gold CSDS indicates.
the RI of the particle is greater than the liquid.
2.
A limited number ( approximately 15) of the 82 naturally occurring zeolite species have
documented fibrous and/or elongate particle morphology.
2. The range of index of refraction values for fibrous elongate zeolites: 1.45-1.52, most
appear to be above 1.47. Reported/documented range of refractive index values for
erionite: 1.455-1.485, depending on major cation (K, Ca, Na) prevalence.
3. 1.48, 1.49 and 1.47 HD RIL’s were made from1.550 Series E and triacetin for assessing
the possibility of differentiating erionite from other fibrous zeolites using CSDS combined
with sign of elongation, extinction angle, morphology and birefringence for erionite
PLM/CSDS screening protocol similar in principle to what is used for asbestos identification.
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Particle Size: 1μm width, 5 μm length. PLM method is not appropriate for
detection or quantification of “respirable” erionite fibers, which requires
SEM and/or TEM assessment of exposure potential.
PLM is not the accepted definitive means for structural identification of
zeolites. (XRD) is required, but has limited detection limit capabilities
based on current technology, and is not without erionite interferences in
complex mineral mixtures such as soils and rock.
CSDS colors can be subdued at 100X magnification due to low
birefringence of erionite particularly with fibers approaching resolution
limits. Commercial 200X and 400X CSDS objectives are limited, can be
fabricated, but require significantly more illumination than standard PLM
microscope configurations in order to observe CSDS colors.
The PLM screening technique may require significantly more knowledge,
experience and resources than what may be available to many analysts
performing traditional environmental PLM/CSDS analyses (asbestos).
Magenta CSDS parallel to
fiber bundle length
indicates match: RI=1.47.
Blue CSDS perpendicular
to fiber bundle length
indicates RI of erionite is
slightly less than 1.47.
Morphology is similar to
polyfilamentous
morphology characteristic
of chrysotile asbestos.
Blue CSDS parallel and
perpendicular indicates RI’s
are slightly less than 1.47.
Indicates compositionally
different compared to
Durkee Oregon erionite.
Morphology is similar to
tremolite-actinolite
asbestos habit, and
discernibly different from
wooly Durkee erionite.
Blue CSDS colors parallel
and perpendicular
indicates RI is slightly
less than 1.47. RI’s and
morphology consistent
compared to Karain,
different compared to
Durkee.
Digital
magnification of
acquired image
accentuates CSDS
better than can be
acquired using
200X or 400X
CSDS objective,
confirming RI’ are
slightly less than
1.47.
Gold CSDS indicates RI is greater than
1.47. Blue magenta CSDS indicates RI
is very slightly less than 1.47. Light
blue CSDS indicates RI is less than
1.47. Distinctly different hexagonal
prism morphology compared to
needle-like Rome/Karain and
polyfilamentous Durkee erionite.
Difference in CSDS along fiber length
indicates compositional variation,
possibly structural variation (possible
erionite intergrowth). Consistent with
TEM EDX analysis.
Magenta blue CSD
perpendicular to fiber
length indicates RI is close
to 1.47. Blue CSD parallel
to fiber length indicates RI
is less than liquid.
Differences in CSDS
compared to erionite
specimens examined.
Mordenite can be further
differentiated from erionite
and offretite on basis of
sign of elongation.
Mordenite (-), erionite (+),
offretite (+/-).
Skookumchuck Mesolite: “Anomalous”
CSDS and morphologically different
from erionite.
Lane Cty Oregon Natrolite: 1.48 CSD
different compared to erionite in 1.48
(light blue). Morphologically similar.
1.48 HD RI can further facilitate differentiation of
fibrous/elongate zeolites
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Rome Oregon and Cappadocia (Karain) Turkey erionite exhibit similar morphologies
(TEM,PLM), chemistry (EDX) and structure (XRD). Suggests Rome Oregon erionite would
serve as a suitable North American reference specimen for comparison to Cappadocia
erionite upon which epidemiology studies for IARC classification is based.
TEM analysis suggests similar EDX patterns with variable chemistry as expected. Si:Al,
Si:K and AL:K appear to suggest consistency and may be useful for differentiation of
erionite from other fibrous zeolites. Further work is required to determine if the
observed patterns are consistent for erionite and different for other fibrous zeolites.
SAED analysis indicates indexable patterns obtainable for potential structural
identification. Further work is required.
Differentiation of erionite from other fibrous/elongate zeolites by 1.47 PLM CSDS
comparison as a screening technique shows promise. If consistency in future analysis is
demonstrated, the technique may be used in conjunction with XRD, SEM and TEM
analysis of specimens for erionite content characterization.
Further CSDS analysis combined with comparison of morphology and optical attributes
(sign of elongation, birefringence) on more erionite & other fibrous/elongate zeolite
specimens is required to demonstrate consistency in observations made to date on the
limited number of specimens examined.