Preparation and Characterization of “Libby Amphibole” 

Toxicological Testing Material

Open-File Report 2012–1012

U.S. Department of the Interior

U.S. Geological Survey
Preparation and Characterization of “Libby Amphibole” 

Toxicological Testing Material

By Heather A. Lowers, Stephen A. Wilson, Todd M. Hoefen, William M. Benzel, and Gregory P. Meeker

Open-File Report 2012–1012

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Suggested citation:

Lowers, H.A., Wilson, S.A., Hoefen, T.M., Benzel, W.M., and Meeker, G.P., 2012, Preparation and characterization 

of “Libby Amphibole” toxicological testing material: U.S. Geological Survey Open-File Report 2012–1012, 20 p.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iv

Contents

Introduction.................................................................................................................................................................... 1

Sample Collection.......................................................................................................................................................... 1

Preparation of the LA2007 Material ............................................................................................................................... 2

Chemical and Mineralogical Analyses ........................................................................................................................... 4

Bulk Chemical Analysis.............................................................................................................................................. 4

X-ray Diffraction Analysis........................................................................................................................................... 4

Electron Probe Microanalysis (EPMA) ....................................................................................................................... 5

Size Characterization................................................................................................................................................. 6

References Cited........................................................................................................................................................... 6

Figures

1. Cumulative frequency distribution of the length, width, and aspect ratio of Libby amphibole in the 

LA2000 mixture. Structures less than 0.8 micrometers (μm) in length and with aspect ratios less than 2.8 

have been removed to better reflect the counting criteria for air sampling methods ............................................... 8

2. Generalized geologic map of the Vermiculite Mountain mine site. Sample locations from 2000 (PE) 

and 2007 (USGS) are shown. Only one of the locations sampled in 2000 was inaccessible during the 2007 

sample collection..................................................................................................................................................... 9

3. Sample collection process for the 2007 material................................................................................................... 10

4. Electron-microprobe-determined amphibole compositions of the individual components of the LA2007 

material compared to the original 30 samples collected in 2000 and the LA2000 composite material.................. 11

5. Customized roller mill. The steel grate holds the ball jar (wrapped in duct tape) in place ..................................... 12

6. Work flow process for characterization and preparation of the LA2007 composite material ................................. 13

7. Comparison of bulk chemistry of LA2000 and LA2007 composite materials as determined by 

ICP-AES-MS......................................................................................................................................................... 14

Tables

1. Sample numbers and locations referenced to WGS 1984 datum that comprise the LA2007 

composite material................................................................................................................................................ 15

2. Weight percentages of phases present in the individual components as well as the mixture based 

on x-ray diffraction analyses. In addition, trace amounts of titanite (CaTi SiO5) were observed during electron 

microprobe analyses............................................................................................................................................. 16

3. Bulk chemical analyses of the individual components of the LA2000 and LA2007 composite 

materials as well as aliquots of the LA2007 composite material (LA2007 A and LA2007 B)................................. 17

4. Electron probe microanalysis of amphibole from the individual samples that compose the 

LA2007 mixture..................................................................................................................................................... 20
1

Preparation and Characterization of “Libby Amphibole” 

Toxicological Testing Material

By Heather A. Lowers, Stephen A. Wilson, Todd M. Hoefen, William M. Benzel, and Gregory P. Meeker 

Introduction

The U.S. Environmental Protection Agency (USEPA) began work in Libby, Mont. in 1999 

when an Emergency Response Team was sent to investigate local concern and media reports 

regarding asbestos-contaminated vermiculite. Since that time, the site has been granted Superfund 

status and site remediation to a safe level of asbestos has been ongoing. The amphibole asbestos 

from the Vermiculite Mountain vermiculite deposit near Libby, Mont. (Libby amphibole) is 

unusual in the sense that it is currently not classified as one of the regulated six asbestos minerals—

chrysotile (a serpentine mineral) and the amphibole minerals amosite (asbestiform cummingtonitegrunerite), crocidolite (asbestiform riebeckite), asbestiform anthophyllite, asbestiform tremolite, 

and asbestiform actinolite. The amphiboles from the Vermiculite Mountain vermiculite deposit, 

primarily winchite and richterite, are related to tremolite and in the past have been referred to as 

sodium-rich tremolite or soda tremolite (Larsen, 1942; Boettcher, 1966; Wylie and Verkouteren, 

2000; Gunter and others, 2003; Meeker and others, 2003). The public health issues in Libby, Mont. 

have brought to light many of the inconsistencies in the literature regarding fiber characteristics,

nomenclature, and toxicology.

To better understand the toxicological characteristics of the Libby amphibole, investigators 

require a sufficient quantity of material representing the range of fibrous amphiboles present in the 

vicinity of Vermiculite Mountain to use in toxicology studies. The material collected in 2000 

(Meeker and others, 2003) has been exhausted and a second collection and preparation effort, 

funded by the USEPA, was conducted in 2007. Both the 2000 (LA2000) and 2007 (LA2007) 

materials were generated to support research needs identified by the USEPA and the National 

Toxicology Program, and new in-vivo and in-vitro toxicology studies are underway. This OpenFile Report describes the process of preparation and summarizes the chemistry and mineralogy of 

the LA2007 toxicological testing material.

Sample Collection

Thirty samples were collected from the Vermiculite Mountain mine site and described by 

Meeker and others (2003). Of those 30 samples, 6 were mixed to produce the LA2000 (also called 

the "six-mix") sample that has been characterized (Bellamy and Gunter, 2008) and used in several 

toxicology-related studies (Blake and others, 2007, 2008; Duncan and others, 2010; Heintz and 

others, 2010; Hillegass and others, 2010; and Smartt and others 2010). The six samples used for the 

LA2000 material correspond to samples 20, 23, 25, 27, 28, and 30 as identified in Meeker and 

others (2003). These six samples were combined to approximate the compositional space of the 

amphibole minerals from the mine (see figures 6 and 7 in Meeker and others, 2003). In addition, 
2

the LA2000 material was ground to approximate the length, width, and aspect ratio of fibers 

reported for the Libby air data (fig. 1) (compare U.S. Environmental Protection Agency, 2010). 

Since the supply of LA2000 has been exhausted, the need to "recreate" this sample 

prompted two sampling trips to the Vermiculite Mountain mine in May and September of 2007 

(fig. 2). Where possible, the same sites sampled in 2000 were re-sampled. One of the sites sampled 

in 2000, sample 28, was inaccessible in 2007 due to slope failure. The first trip in May 2007 was a 

reconnaissance trip to collect small samples for analysis in order to determine the best sample site 

locations to approximate the LA2000 sampling material based on amphibole chemistry, 

mineralogy, morphology, and minimizing accessory phases. The eight samples collected in May 

were returned to the USGS analytical laboratories and analyzed by electron microprobe and x-ray 

diffraction. 

Based on analytical results from the May reconnaissance trip, approximately 300 kilograms 

(kg) of amphibole-rich rock was collected at the Libby mine in September of 2007. Samples were 

collected by removing amphibole-rich rock from veins in cut faces and from large boulders in 

previously mined areas of the property. Amphibole-rich rock was removed using stainless steel 

chisels either by hand or with chipping hammers and returned to a base camp set up on the mine 

property (fig. 3A). At the base camp (fig. 3B), larger pieces of material were placed on a large 

plastic sheet and further reduced in size using chisels and sledge hammers (fig. 3C). The most 

amphibole-rich material was then placed in a large steel shatter box and reduced to gravel-size 

pieces or smaller using a sledge hammer. During this process, pieces of rock that contained 

significant visible amounts of contaminants such as pyroxene, biotite, and vermiculite were 

removed.

After reducing the sample material to gravel-size or less, the material was sieved and put 

through a jaw crusher to reduce the material to millimeter-size or less (fig. 3D). Representative 

aliquots of the reduced material for each sample were removed and placed in plastic zip-lock bags 

for analysis by X-ray diffraction (XRD), electron probe microanalysis (EPMA), scanning electron 

microscope-energy dispersive spectroscopy (SEM/EDS), and inductively coupled plasma mass 

spectrometry (ICP-MS) at the USGS laboratories in Denver, Colo. The reduced material from 

individual sample sites was then placed in double plastic bags, weighed, and sealed into 5-gallon 

(gal) pails for shipment. Of the eight samples returned, a mixture of three was chosen to best 

approximate the chemical and morphological variation of the LA2000 material (see analyses 

below). Table 1 lists the coordinates of the three samples chosen for the LA2007 material.

Preparation of the LA2007 Material

Based on EPMA and XRD analyses of the May 2007 reconnaissance samples and 

representative aliquots of the September 2007 samples referred to in the preceding section, three 

individual samples were chosen to comprise the mixture. The individual samples 070917-1, 

070918-5, and 070920-2 were chosen to prepare the 2007 Libby amphibole material because they 

contain the least contaminants (table 2) and provided a similar distribution of data points in the 

compositional space reported by Meeker and others 2003 (fig. 4) (see following data). The weight 

percentages of each sample were determined to provide the best match possible to the overall 

chemistry and mineralogy of the amphibole in the mine and the composition of the LA2000 

sample. It was determined that LA20007 should be mixed in the following proportions: 90 percent 

by weight of sample 070918-5 (primarily winchite) and 5 percent by weight each of samples 

070917-1 (primarily tremolite) and 070920-2 (primarily richterite and winchite). The goal was to 

produce approximately 10 kg of the composite amphibole material.
3

The individual samples from the 5-gal buckets packaged in Libby (described above) were 

processed at the U.S. Geological Survey (USGS) facilities in Lakewood, Colo., in a negativepressure room specifically designed for working with asbestiform minerals. Approximately two 

liters of crushed, reduced material and three liters of deionized water were transferred to a 1-gal 

stainless steel, four-speed Waring commercial blender (model 31BL79). The mixture was 

processed for approximately 2 minutes (min) at the lowest speed. The blended slurry was then 

quantitatively transferred to a five gallon container lined with a plastic bag. This procedure was 

repeated until the correct amount of each specific amphibole needed for the final material was 

processed.

Aliquots of this “chopped” material were then ground using a 10-liter (L) ceramic ball jar 

filled with 3⁄4-inch (in) alumina grinding cylinders and a customized USGS horizontal roller mill 

(fig. 5). In this procedure, approximately 2 L of “chopped” material were transferred to the ball jar 

along with 3 L of deionized water. The jar was sealed, its outside surfaces wiped clean and the jar 

transferred to the horizontal roller mill located adjacent to the hood. The roller mill was operated at 

approximately 20 rotations per minute for a period of 6 hours (hr). The duration of the grinding 

period was controlled using a commercial timer.

After the grinding period, the ball jar was transferred back to the asbestos hood. The 

asbestos suspension was separated from the grinding media and transferred to a 5-gal container 

lined with a plastic bag. The alumina grinding cylinders were rinsed and the rinse solution was 

transferred to the 5-gal asbestos container. The grinding cylinders were then transferred back to the 

ball jar along with a second aliquot of “chopped” amphibole and a new supply of deionized water.

After the second round of grinding, the liquid used in grinding was switched from deionized water 

to the supernatant solution from the ground asbestos container following a 6-hr settling period. This 

recycled water was clear and contained no obvious signs of suspended amphibole material. The 

supernatant was removed from the 5-gal asbestos container using a siphon process which 

minimized any disturbance of the ground amphibole material during removal. Use of this recycled 

water helped minimize the amount of contaminated water that would require processing during 

later stages of material preparation.

For each individual sample, after grinding was completed, the container of processed 

material was allowed to evaporate to dryness. After the samples reached apparent dryness, the 

container was sealed, its outside surfaces wiped clean with paper towels, and the container was 

transferred to a plastic trash bag which was then sealed. The bag containing the asbestos samples 

were removed from the hood and weighed to obtain an estimate of the sample mass. Prior to the 

final blending stage, a percent moisture determination was performed on the three individual 

processed asbestos types. The percent moisture value was determined by taking 5 aliquots of each 

asbestos sample using a sample thief and combining the aliquots in a pre-weighed glass bottle.

Bottle weights before and after drying (110°C) were obtained in order to estimate the percent 

moisture content of each container. To achieve the desired blending ratio of the three asbestos 

samples, a calculated amount of each sample, taking into account water content, was combined in 

an unlined 5-gal container. Deionized water was added to the 5-gal container to obtain a fluid 

suspension that was easily mixed. All blending was performed using a cordless drill equipped with 

a standard commercial paint mixer. Blending typically lasted for a period of 10 min at low to 

moderate drill speed. A total of three batches of blended material was prepared in this manner. To 

ensure the consistency of the final material, aliquots of each batch were transferred in a random 

manner between the other containers and then briefly mixed.
4

In the final preparation step, aliquots from each container were randomly transferred to a 

4-in x 9-in x 16-in stainless steel drying pan on a standard laboratory hot plate. The hot plate was 

fitted with an aluminum foil tent to prevent splatter, and the material was allowed to evaporate to 

dryness, usually overnight. After drying, the contents of the pan were lightly disaggregated and 

then transferred to a plastic lined 5-gal container. This process was repeated until the desired 

amount (roughly 10 kg) of blended material was obtained. A summary of the process is presented 

in figure 6. 

Chemical and Mineralogical Analyses

Bulk Chemical Analysis

Inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ICP-MS were 

performed on the three individual samples that went into the LA2007 composite material as well as 

on two aliquots of the LA2007 composite material. ICP-MS was performed with a Perkin-Elmer 

Model 6000 ICP-MS following a four acid (nitric, perchloric, hydrofluoric, and hydrochloric) 

dilution of the material (Briggs and Meier, 1999). Refractory phases such as chromite, zircon, and 

rare earth element-bearing phases may not completely dissolve in the acid digestion. For this 

reason, the sample was decomposed at 450°C in a sodium peroxide sinter for ICP-AES-MS.

Because a sodium peroxide sinter is used, sodium (Na) and silicon (Si) are not analyzed by ICPAES-MS. Additional analytical methods were used to measure elements gold (Au), mercury (Hg), 

selenium (Se), and tellurium (Te); however, these elements were below the detection limit of the 

method. The procedures for all methods are described at 

http://minerals.cr.usgs.gov/projects/analytical_chem/references.html. 

The results of the bulk methods are summarized in table 3 and figure 7. The results are for 

informational purposes only and do not represent certified values. Few elements vary between the 

LA2000 and LA2007 samples. The notable differences are higher strontium, phosphorus, copper, 

niobium, and molybdenum in the LA2000 sample. These differences are explained by the presence 

of various accessory minerals such as celestine (SrSO4), fluorapatite (Ca5PO4F), chalcopyrite 

(CuFeS2), and in the LA2000 which were not observed in the individual samples that went into the 

LA2007. 

X-ray Diffraction Analysis

For X-ray Diffraction, a 2-gram aliquot of the processed individual and composite samples 

was passed through a 60-mesh sieve and then side packed into a PANalytical sample holder for 

analysis. The samples were scanned using the following conditions: 

PANalytical “X’Pert Pro – MPD X-ray Diffractometer

Theta/Theta geometry

Cu long-fine-focus X-ray tube (nickel (Ni) filtered) 

“X’celerator” solid state “strip” detector

instrument conditions are 45 kV, 40 mA 

15 millimeter beam mask 

1⁄2° anti-scatter slit

1⁄4° divergence slit 
5

1⁄2° receiving anti-scatter slit 

1⁄4° receiving divergence slit

step size 0.0167 degrees in continuous scan mode 

scan range of 5 to 65 (or 90) degrees two-theta

sample spinner on

scan rate was 1 degree per minute for a total scan time of 1 hr

Identification of mineral phases was made using Material Data Inc. (MDI) Jade (V 9.1) 

search-match software using the International Center for Diffraction Data (ICDD) “2009 PDF-4” 

and National Institute of Standards and Technology “FIZ/NIST Inorganic ICSD” databases. Semiquantitative mineral estimates were calculated using MDI Whole Pattern Fit (WPF) software which 

simultaneously calculates a whole pattern fit and a Rietveld refinement of the minerals. Reference 

minerals are selected from the database, some of which are “structure” references that represent 

ideal crystals of the mineral, and other entries are real-world mineral specimens. Each of these 

cards contains a full crystallographic description of the mineral. A calculated model of the observed 

pattern is produced by non-linear, least-squares optimization. The calculations, performed by the 

software, involve the application of various parameters to improve the fit of the model to the 

observed data. Modeling parameters include background reduction, profile fitting, and lattice 

constants that iterate to minimize a residual error between the calculated x-ray diffraction pattern 

from the selected references in comparison to the measured scan of the sample. All data were 

normalized to 100 percent based on the identified minerals. A full description of the WPF

algorithm is available from MDI (Materials Data Inc., 2011).

X-ray diffraction analysis measures the crystalline portion of the sample. This does not 

include any amorphous phases that may be present. The WPF software normalizes the data to 100

percent for all identified phases. The typical detection limit by X-ray diffraction is between 1 and 3 

weight percent (wt %), depending on the crystallinity of the phase and interferences from 

overlapping lines from other phases. Thus, there may be trace phases present, but not identified and 

they are not included in the model. The phases identified and their estimated weight percentages are 

given in table 2. Also included in table 2 are phases observed in polished thin sections during 

electron probe microanalysis but not detected by XRD.

Electron Probe Microanalysis (EPMA)

Quantitative EPMA of polished thin sections was performed using a five-wavelength 

spectrometer (WDS), fully automated, JEOL 8900 scanning electron microprobe, at the USGS in 

Denver, Colo. Analytical conditions were: 15 kilovolt (kV) accelerating voltage, 20 nanoampere 

(nA) beam current (cup), point beam mode, and 20-second (sec) peak, and 10-sec background 

counting time. Calibration was performed using well-characterized silicate and oxide standards. 

Analytical precision for major and minor elements based on replicate analysis of standards was 

better than plus or minus 2 percent relative concentration for major and minor elements and equal 

to counting statistics for trace (less than 1 wt%) elements. Oxide weight percent values were 

converted to cations based on 23 oxygen equivalents using the recommendations of Leake and 

others (1997). The chemical analyses and calculated mineral formula are summarized in table 4 and 

figure 4. Multiple analyses were acquired on each sample. The quality of the data depended largely 

on the fibrosity of the material. More fibrous material yielded lower quality data; thus, fewer 

analyses are averaged for each sample.
6

Size Characterization

Given that researchers working with the LA2007 composite material will likely conduct 

their own analyses to characterize fiber size distributions, it was determined that a size 

characterization of the LA2007 material was unnecessary at this time. The LA2000 and LA2007 

composite materials were provided to the USEPA laboratories in Research Triangle Park, N.C. for 

water elutriation following the methods in Webber and others (2008). The elutriation was 

performed to create a material for intratracheal installation and in vitro toxicology studies that 

would closely match a rat-respirable fiber size distribution. The method for particle counting the 

water-elutriated material is described in Lowers and Bern (2010). The water-elutriated LA2007 

material contained 98 percent particles with an aspect ratio greater than or equal to 5, mean length 

of 4.99 plus or minus 4.53 μm and mean width of 0.28 plus or minus 0.19 μm, with upper and 

lower values of length and width being 0.52–27.30 μm and 0.07–1.15 μm, respectively, as 

determined using transmission electron microscopy (Shannahan and others, 2011).

References Cited

Briggs, P.H., and Meier, A.L., 1999, The determination of forty-two elements in geological 

materials by inductively coupled plasma-mass spectrometry: U.S. Geological Survey Open-File 

Report 99–166.

Bellamy, J.M., and Gunter, M.E., 2008, Morphological characterization of Libby “six-mix” 

amphiboles used in in vivo studies: Periodico Di Mineralogia, vol. 77, no. 2, p. 75–82.

Blake, D.J., Bolin, C.M., Cox, D.P., Cardozo-Pelaez, F., and Pfau, J.C., 2007, Internalization of 

Libby amphibole asbestos and induction of oxidative stress in murine macrophages: Toxicology 

Sciences, vol. 99, no. 1, p. 277–288.

Blake, D.J., Wetzel, S.A., and Pfau, J.C., 2008, Autoantibodies from mice exposed to Libby 

amphibole asbestos bind SSA/Ro52-enriched apoptotic blebs of murine macrophages: 

Toxicology, vol. 246, no. 2-3, p. 172–179.

Boettcher, A.L., 1966, The Rainy Creek igneous complex near Libby, Montana: University Park, 

Penn., Pennsylvania State University, Ph.D. thesis, 155 p.

Duncan, K.E., Ghio, A.J., Dailey, L.A., Bern, A.M., Gibbs-Flournoy, E.A., Padilla-Carlin, D.J., 

Roggli, V.L., and Devlin, R.B., 2010, Effect of size fractionation on the toxicity of amosite and 

Libby amphibole asbestos: Toxicology Science, vol. 118, no. 2, p. 420–434.

Gunter, M.E., Dyar, D.M., Twamley, B., Foit, F.F. Jr., and Cornelius, S., 2003, Composition, 

Fe3

+/Fe, and crystal structure of non-asbestiform and asbestiform amphiboles from Libby, 

Montana, U.S.A.: American Mineralogist, vol. 88, no. 11-12, part 2, p 1970–1978.

Heintz, N.H., Janssen-Heininger, Y.M.W., and Mossman, B.T., 2010, Asbestos, lung cancers, and 

mesotheliomas from molecular approaches to targeting tumor survival pathways: American 

Journal of Respiratory Cell and Molecular Biology, vol. 42, no. 2, p. 133–139.
7

Hillegass, J.M., Shulka, A., MacPherson, M.B., Lathrop, S.A., Alexeeva, V., Perkins, T.N., van der 

Vliet, A., Vacek, P.M., Gunter, M.E., and Mossman, B.T., 2010, Mechanisms of oxidative stress 

and alterations in gene expressions by Libby six-mix in human mesothelial cells: Particle and 

Fibre Toxicology, doi:10.1186/1743-8977-7-26, p. 7–26. 

Larsen, E.S., 1942, Alkalic rocks of Iron Hill, Gunnison County, Colorado: U.S. Geological Survey 

Professional Paper 197-A, 64p. 

Leake, B.E., Woolley, A.R., Arps, C.E.S., Birch, W.D., Gilbert, M.C., Grice, J.D., Hawthorne, 

F.C., Kato, A., Kisch, H.J., Krivovichev, V.G., Linthout, K., Laird, J., Mandarino, J.A., Maresch, 

W.V., Nickel, E.H., Rock, N.M.S., Schumacher, J.C., Smith, D.C., Stephenson, N.C.N., 

Ungaretti, L., Whittaker, E.J.W., and Youzhi, G., 1997, Nomenclature of the amphiboles—

Report of the subcommittee on amphiboles of the International Mineralogical Association, 

Commission on New Minerals and Mineral Names: American Mineralogist, v. 82, p. 1019–1037. 

Lowers, H.A., and Bern, A.M., 2009, Particle size characterization of water-elutriated Libby 

amphibole 2000 and RTI international amosite: U.S. Geological Survey Open-File Report 

2009–1242, 3 p. (Also available at http://pubs.usgs.gov/of/2009/1242/.) 

Materials Data Inc., 2011, Materials data: Livermore, Calif., Materials Data Inc., accessed online 

June 8, 2011, at http://www.materialsdata.com. 

Meeker, G.P., Bern, A.M., Brownfield, I.K., Lowers, H.A., Sutley, S.J., Hoefen, T.M., and Vance, 

J.S., 2003, The composition and morphology of amphiboles from the Rainy Creek Complex, near 

Libby, Montana: American Mineralogist, vol. 88, no. 11-12, part 2, p.1955–1969. 

Shannahan, J., Schladweiler, M., Padilla-Carlin, D., Nyska, A., Richards, J., Ghio, A., Gavett, S., 

and Kodavanti, U., 2011, The role of cardiovascular disease-associated iron overload in Libby 

amphibole-induced acute pulmonary injury and inflammation: Inhalation Toxicology, v. 23, 

p. 129–141. 

Smartt, A.M., Brezinski, M., Trapkus, M., Gardner, D., and Putnam, E.A., 2010, Collagen 

accumulation over time in the murine lung after exposure to crocidolite asbestos or Libby 

amphibole: Environmental Toxicology, v. 25, p. 68–76. 

 U.S. Environmental Protection Agency, 2010, Particle size distribution data for Libby Amphiboles 

structures observed in air at the Libby Asbestos Superfund Site: U.S. Environmental Protection 

Agency, Denver, Colo., Superfund Records Center, HERO ID 759201. 

Webber, J.S., Blake, D.J., Ward, T.J., and Pfau, J.C., 2008, Separation and characterization of 

respirable amphibole fibers from Libby, Montanan: Inhalation Toxicology, v. 20, no. 8, 

p. 733–740. 

Wylie, A.G. and Verkouteren, J.R., 2000, Amphibole asbestos from Libby, Montana—Aspects of 

nomenclature: American Mineralogist, vol. 85, p. 1540–1542. 
8

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.1 1.0 10.0 100.0

LENGTH IN MICROMETERS

CUMULATIVE DISTRIBUTION FREQUENCY

 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0 0.1 1.0 10.0

WIDTH IN MICROMETERS

CUMULATIVE DISTRIBUTION FREQUENCY

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.1 1.0 10.0 100.0

ASPECT RATIO

CUMULATIVE DISTRIBUTION FREQUENCY

Figure 1. Cumulative frequency distribution of the length, width, and 

aspect ratio of Libby amphibole in the LA2000 mixture. Structures 

less than 0.8 micrometers (μm) in length and with aspect ratios less 

than 2.8 have been removed to better reflect the counting criteria for 

air sampling methods.
9

Figure 2. Generalized geologic map of the Vermiculite Mountain mine site. Sample locations from 2000 (PE) and 2007 (USGS) are shown. Only 

one of the locations sampled in 2000 was inaccessible during the 2007 sample collection.
10

Figure 3. Sample collection process for the 2007 material. A, Removing material from an amphibole-rich vein. B, Base camp constructed near site 

USGS070918-5 to process samples prior to shipping. The base camp was built to contain the release of the fibers to the air during processing.

C, Material was further reduced with sledge hammers and chisels until it was small enough to fit in the jaw crusher, D. 
11

Libby Amphibole Compositions

Diagram Parameters: Si (T) > 7.5, Mg# >0.5

For those amphibole that plot in the tremolite field Mg#>0.9

0

0.5

1

0 0.5 1 1.5 2

SODIUM (Na) IN THE B SITE

SODIUM (Na) PLUS POTASSIUM (K) IN THE A SITE

30 samples

collected in 2000

LA2000 composite

070917-1

070918-5

070920-2

Magnesioarfvedsonite

Magnesioriebeckite

Edenite Richterite

Tremolite

Winchite

Figure 4. Electron-microprobe-determined amphibole compositions of the individual components of the LA2007 material compared to the original 

30 samples collected in 2000 and the LA2000 composite material. Square legends symbols represent samples collected in 2000 and round 

symbols represent samples collected in 2007.
12

Figure 5. Customized roller mill. The steel grate holds the ball jar (wrapped in duct tape) in place.
13

Figure 6. Work flow process for characterization and preparation of the LA2007 composite material. 

[SEM/EDS, Scanning Electron Microscope-Energy Dispersive Spectroscopy; EPMA, electron probe

microanalysis; XRD, X-ray diffraction; L, liter; rpm, rotations per minute; ICP-MS, Inductively coupled 

plasma mass spectrometry]
14

ICP_AES_MS

0.01

0.1

1

10

100

1000

Li

Be

Na

MgAl

PK

Ca

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

GaGe

As

Se

Rb

Sr

Y

Zr

Nb

Mo

Ag Cd

In

SnSb

Te

Cs

Ba

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy Ho

Er

Tm

Yb

Lu

Hf

Ta

W

Re

Au

Tl

Pb

Bi

Th

U

ELEMENT

PARTS PER MILLION (PPM)

LA2007

LA2000

Figure 7. Comparison of bulk chemistry of LA2000 and LA2007 composite materials as determined by ICP-AES-MS.
15

Table 1. Sample numbers and locations referenced to the World Geodetic System WGS 1984 datum that 

comprise the LA2007 composite material. 

May 2007 sample Equivalent September 

2007 sample

Long_WGS84 Lat_WGS84

USGS070531-11 070920-2 -115.406672 48.43606235

USGS070530-2 070917-1 -115.3982966 48.43273905

USGS070531-13-2 070918-5 -115.4008729 48.43804663
16

Table 2. Weight percentages of phases present in the individual components as well as the mixture based on x-ray diffraction analyses. In addition, 

trace amounts of titanite (CaTi SiO5) were observed during electron microprobe analyses. [ND, nondetect] 

Phase General Formula 070917-1 070918-5 070920-2 LA2007-A LA2007-B 

Amphibole (K,Na)(Na,Ca)2(Mg,Fe)5Si8O22(OH,F,Cl)2 66 84 51 84 84

Calcite CaCO3 18 ND 24 3 4

Talc Mg3(Si4O10)(OH)2 11 8 ND 2 1 

Vermiculite (Mg,Fe,Al)2(Al,Si)4O10(OH)2.4(H2O) 5 ND ND ND 1

Orthoclase KAlSi3O8 ND 7 5 7 8

Quartz SiO2 ND ND 12 2 1 

Dolomite MgCa(CO3)2 ND ND 5 1 1

Biotite K(Mg,Fe)3Al[Si3O10](OH,Cl,F) ND ND 3 ND ND
17

Table 3. Bulk chemical analyses of the individual components of the LA2000 and LA2007 composite materials as well as aliquots of the LA2007 composite material

(LA2007 A and LA2007 B). [ICP-MS, Inductively coupled plasma mass spectrometry; ICP-AES, Inductively coupled plasma atomic emission spectrometry; ICPACID, total acid digestion; ppm, parts per million; na, not applicable]

Year 

Analyzed

Feb

2010

Feb

2010

Feb

2010

Feb

2010

Feb

2010

2001 2001 2001 2001 2001 2001 Dec

2010

Jan

2011

Sample LA2007 

A

LA2007 

B

0709-18-

5-win

0709-20-

2-ric

0709-17-

1-trem

20B 23B 25B 27B 28B 30B LA2000 LA2000

Bulk 

chemical 

method 

listed, 

otherwise ICPMS-AES

Atomic 

Number

Element Unit ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICPAES

_MS_55

3 Li ppm 10 <10 <10 20 20 6.1 4 3 0.7 17 2 9.8 10

4 Be ppm <5 <5 <5 <5 <5 0.2 0.4 2.1 0.8 1.8 0.4 4.8 <5

11 Na % NA NA NA NA NA 0.83 1.4 1.8 0.85 1.8 2.5 2.03 na

12 Mg % 11.6 11.4 12.7 7.93 9.71 4.3 5.7 7.1 4.1 7.9 7.2 1.07 10.3

13 Al % 0.88 0.82 0.75 0.65 0.49 0.28 0.4 0.4 0.06 1.7 1 0.946 1.26

15 P % 0.01 0.01 0.01 <0.01 0.02 0.02 0.02 < 0.01 0.04 < 0.01 0.04 0.0665 0.07

19 K % 1.34 1.34 1.31 1.38 0.56 0.27 0.8 1 0.26 1.4 2.1 1.34 1.6

20 Ca % 6.94 6.88 6.49 12.8 11.3 16 14 8.5 20 3.9 4 1.01 10.7

21 Sc ppm 83 81 90 68 57 48 61 34 62 66 110 74.3 68

22 Ti % 0.18 0.18 0.21 0.15 0.14 0.1 0.07 0.1 0.1 0.2 0.2 0.207 0.22

23 V ppm 94 92 103 149 30 9 17 83 45 130 66 205 206

24 Cr ppm 680 680 710 1070 440 400 480 420 130 390 50 633 590

25 Mn ppm 900 900 900 800 800 590 610 410 460 500 740 875 800

26 Fe % 3.95 3.93 4.39 2.5 2.93 2.1 2.8 2.8 1.4 3.6 3.6 3.41 3.35

27 Co ppm 34.9 38.9 21.6 22.5 29.9 23 27 38 12 43 38 38.2 37.9

28 Ni ppm 118 116 124 78 92 43 46 110 26 88 49 86.9 90

C_ICP1

0

29 Cu ppm 5.84 6.87 5.24 16.5 1.74 < 3 10 6 20 8 < 3 16.1 15

30 Zn ppm 52 45 46 50 39 10 20 30 10 51 30 50.4 38

31 Ga ppm 3 3 1 4 1 1.1 1.4 2.5 0.4 6.5 3.9 4.9 5

32 Ge ppm 3 3 2 2 3 1.2 2 2.2 1.6 1.2 1.9 na 3

C_ICP1

0

33 As ppm <1 <1 <1 <1 <1 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 <1 <30

C_Se 

Hyd

34 Se ppm <0.2 <0.2 <0.2 <0.2 <0.2 < 1 < 1 < 1 < 1 < 1 < 1 na na

37 Rb ppm 10.2 10.3 5.2 10.5 8.6 6.1 9.8 8.9 0.9 38 16 18.6 17.9

38 Sr ppm 149 142 42.9 1230 291 480 470 270 510 73 35 535 589

39 Y ppm 2 2.2 0.9 3.9 1.3 3.4 2.5 1.2 2.1 3.2 4.5 3.9 2.9

40 Zr ppm 6.6 6.5 2.6 10.8 2.8 na na na na na na na 8

41 Nb ppm 1 1 <1 3 <1 0.1 0.1 1.5 1 2.3 0.4 7.1 4
18

Year 

Analyzed

Feb

2010

Feb

2010

Feb

2010

Feb

2010

Feb

2010

2001 2001 2001 2001 2001 2001 Dec

2010

Jan

2011

Sample LA2007 ALA2007 B0709-18-

5-win

0709-20-

2-ric

0709-17-

1-trem

20B 23B 25B 27B 28B 30B LA2000 LA2000

Bulk 

chemical 

method 

listed, 

otherwise ICP

-

MS-AES

Atomic 

Number

Element Unit ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICP_ACI

D 

ICP_ACI

D 

ICP_ACI

D 

ICP_ACI

D 

ICP_ACI

D 

ICP_ACI

D 

ICP_ACI

D 

ICPAES

_MS_55

C_ICP1 042 Mo ppm 0.6 0.3 0.3 0.5 0.3 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 <0.05 <2

C_ICP1

0 

47 Ag ppm 0.73 0.65 0.46 2.19 0.55 < 0.02 < 0.02 < 0.02 < 0.02 < 0.02 < 0.02 0.028 <1

C_ICP1 048 Cd ppm 0.16 0.15 0.15 0.2 0.11 < 0.1 0.1 < 0.1 0.1 0.1 < 0.1 <0.007 <0.2

49 In ppm <0.2 <0.2 <0.2 <0.2 <0.2 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 na <0.2

50 Sn ppm <1 <1 <1 <1 <1 < 0.5 < 0.5 0.7 0.8 0.6 < 0.5 na 25

51 Sb ppm 0.2 0.3 0.2 0.3 <0.1 < 0.1 < 0.1 0.1 < 0.1 < 0.1 < 0.1 <0.04 0.1

C_Te 

Hyd

52 Te ppm <0.5 <0.5 <0.5 <0.5 <0.5 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 na NA 55 Cs ppm 0.3 0.3 <0.1 0.3 0.6 0.7 0.2 0.2 0.2 2.1 0.2 0.87 0.8

56 Ba ppm 206 202 69.1 1570 195 64 120 47 47 560 370 294 285

57 La ppm 3.3 3.5 1.4 9.9 1.8 3.6 1.8 3.5 5.7 9.2 6.9 8.17

58 Ce ppm 5.8 6.3 2.8 13.9 4.3 8.6 5.4 4.7 6.4 12 14 12 11

59 Pr ppm 0.91 0.97 0.44 1.46 0.75 1.3 0.94 0.52 0.76 1.2 2.3 1.7 1.34

60 Nd ppm 4.5 4.8 2.46 3.9 6.9 5.2 2.3 3.85 127 6.4

62 Sm ppm 1.2 1.3 0.6 1.3 1.1 1.6 1.4 0.56 0.96 1 2.8 1.6 1.2

63 Eu ppm 0.28 0.34 0.15 0.3 0.24 0.44 0.38 0.16 0.27 0.3 0.74 0.42 0.35

64 Gd ppm 0.83 1.04 0.45 1.03 0.83 1.31 0.42 0.74 0.842 1.3 1.06

65 Tb ppm 0.11 0.1 <0.05 0.12 0.09 0.14 0.12 0.05 0.083 0.098 0.22 0.19 0.09

66 Dy ppm 0.52 0.53 0.27 0.61 0.34 0.74 0.6 0.26 0.42 0.59 1.1 0.75 0.56

67 Ho ppm 0.08 0.09 <0.05 0.12 0.06 0.13 0.1 0.04 0.071 0.11 0.18 0.14 0.07

68 Er ppm 0.2 0.23 0.07 0.35 0.15 0.31 0.22 0.11 0.18 0.3 0.39 0.46 0.27

69 Tm ppm <0.05 <0.05 <0.05 <0.05 <0.05 0.04 0.03 0.02 0.02 0.04 0.055 0.065 <0.05

70 Yb ppm 0.2 0.2 0.1 0.4 0.1 0.2 0.2 0.09 0.1 0.3 0.3 0.36 0.2

71 Lu ppm 0.12 0.18 0.07 0.13 0.06 na na na na na na na 0.06

72 Hf ppm <1 <1 <1 <1 <1 na na na na na na na <1

73 Ta ppm <0.5 <0.5 <0.5 <0.5 <0.5 na na na na na na na <0.5

74W ppm <1 <1 <1 <1 <1 < 0.2 < 0.2 < 0.2 < 0.2 < 0.2 < 0.2 0.02 <1

75 Re ppm na na na na na < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 na NA

C_ICP1

0 

79 Au ppm <0.1 <0.1 <0.1 <0.1 <0.1 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 na NA

81 Tl ppm <0.5 <0.5 <0.5 <0.5 <0.5 0.1 < 0.1 < 0.1 0.2 0.3 0.5 0.21 <0.5

C_ICP1

0 

82 Pb ppm55472 2.1 2.4 4.2 1.9 3.73 8.928

83 Bi ppm <0.1 <0.1 <0.1 <0.1 <0.1 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 <0.06 <0.1
19

Year 

Analyzed

Feb

2010

Feb

2010

Feb

2010

Feb

2010

Feb

2010

2001 2001 2001 2001 2001 2001 Dec

2010

Jan

2011

Sample LA2007 

A

LA2007 

B

0709-18-

5-win

0709-20-

2-ric

0709-17-

1-trem

20B 23B 25B 27B 28B 30B LA2000 LA2000

Bulk 

chemical 

method 

listed, 

otherwise ICPMS-AES

Atomic 

Number

Element Unit ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICPAES

_MS_55

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICP_ACI

D

ICPAES

_MS_55

90 Th ppm 0.4 0.3 0.1 0.5 <0.1 0.08 < 0.06 0.1 < 0.06 0.44 0.2 0.55 0.5

92 U ppm 0.45 0.45 0.21 0.34 0.18 0.09 0.2 0.3 0.4 0.59 0.2 0.44 0.32
20

Table 4. Electron probe microanalysis of amphibole from the individual samples that compose the LA2007 mixture.

[Wt %, weight percent; AVG, average]

Wt % 070917-1 

AVG (n=7)

2 Sigma 070918-5 

AVG (n=32)

2 Sigma 070920-2 

AVG (n=10)

2 Sigma

SiO2 55.8 2.92 56.5 2.60 56.2 1.94

TiO2 0.10 0.07 0.24 0.20 0.13 0.22

Al2O3 0.15 0.27 0.22 0.19 0.22 0.27

Cr2O3 NA NA 0.07 0.04 0.23 0.21

FeO 4.88 3.02 5.81 0.67 3.13 2.08

MnO 0.09 0.06 0.09 0.04 0.11 0.05

MgO 20.8 3.05 20.6 0.88 21.8 1.57

CaO 9.56 2.42 7.13 1.32 9.12 2.24

Na2O 2.19 1.18 3.67 0.84 2.92 1.73

K2O 0.49 0.17 1.39 0.56 0.96 0.84

F 0.03 0.08 0.13 0.11 0.50 0.61

Cl 0.03 0.07 0.01 0.03 0.01 0.05

O=F,Cl 0.02 0.04 0.06 0.04 0.21 0.25

TOTAL 94.1 4.33 95.8 3.68 95.1 2.42

Structural Formula

Si 7.985 0.034 7.982 0.025 7.979 0.043

Aliv 0.015 0.034 0.018 0.025 0.021 0.043

Sum T 8.000 0.000 8.000 0.000 8.000 0.000

Alvi 0.010 0.010 0.019 0.017 0.016 0.023

Ti 0.011 0.008 0.025 0.020 0.014 0.024

Fe3+ 0.231 0.268 0.374 0.324 0.121 0.109

Cr 0.000 0.000 0.005 0.009 0.010 0.030

Mg 4.443 0.443 4.331 0.173 4.621 0.221

Fe2+ 0.306 0.229 0.246 0.209 0.216 0.215

Mn 0.000 0.000 0.000 0.001 0.001 0.006

Sum C 5.000 0.000 5.000 0.000 5.000 0.000

Mg 0.000 0.000 0.000 0.000 0.000 0.000

Fe2+ 0.051 0.138 0.067 0.139 0.035 0.063

Mn 0.011 0.007 0.011 0.005 0.012 0.009

Ca 1.464 0.311 1.080 0.212 1.386 0.334

Na 0.474 0.315 0.843 0.301 0.567 0.316

Sum B 2.000 0.000 2.000 0.000 2.000 0.000

Na 0.137 0.071 0.162 0.153 0.238 0.171

K 0.089 0.032 0.251 0.099 0.174 0.152

Sum A 0.226 0.077 0.412 0.149 0.412 0.307

Total 

Cation

15.226 0.077 15.412 0.149 15.412 0.307