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Erionite
General
Category Zeolite mineral
Chemical formula (Na2,K2,Ca)2Al4Si14O 36·15H2O
Identification
Color White, Green, Gray, Orange
Crystal habit Acicular - Occurs as needle-like crystals.
Crystal system Hexagonal, (6/m 2/m 2/m)
Cleavage [010] Distinct
Fracture Splintery
Mohs scale hardness 3.5-4
Luster Vitreous - silky
Streak white
Specific gravity 2.09 - 2.13
Optical properties Uniaxial (-)
Refractive index nω = 1.4711, nε = 1.474
Birefringence δ = 0.0191
Other characteristics non-magnetic, non-radioactive
References [1]

Erionite is a naturally occurring fibrous mineral that belongs to a group of minerals called zeolites. It usually is found in volcanic ash that has been altered by weathering and ground water. Erionite forms brittle, wool-like fibrous masses in the hollows of rock formations and has an internal molecular structure similar to chabazite. Some properties of erionite are similar to the properties of asbestos; however, erionite is not currently regulated by the U.S. Environmental Protection Agency as one of the six asbestos fibers.[2] Erionite was first described by A.S. Eakle in 1898, as white woolly fibrous masses in cavities in rhyolite lava near Durkee, Oregon. It was originally thought to be another relatively rare zeolite named offretite, which is very similar to erodinite in appearance and chemical composition.[3]

Contents

Properties

The chemical composition of erionite is approximately represented by the formula (Na2,K2,Ca)2Al4Si14O 36·15H2O. Erionite has a hexagonal, cage-like structure composed of a framework of linked tetrahedra. It consists of white prismatic crystals in radiating groups of crystal fiber. Erionite absorbs up to 20% of its weight in water, has a specific gravity of 2.02 to 2.13, and has gas absorption, ion exchange, and catalytic properties that are highly selective and depend on the molecular size of the absorbed compounds.[4] Zeolites, in general, have good thermal stability, rehydration kinetics, and water vapor adsorption capacity.

Carcinogenicity

Erionite is known to be a human carcinogen and is listed by the International Agency for Research on Cancer as a Group 1 Carcinogen.[5] The prevalence of malignant mesothelioma due to erionite exposure in the Central Anatolia Region is very high.[6] Descriptive studies have reported an excess of mortality from mesothelioma in individuals living in three Turkish villages where there was chronic exposure to erionite; only two cases of mesothelioma occurred in the control village, both in women born elsewhere. [7] [8] An excess of lung cancer also was reported in two of the three villages contaminated with erionite. Respirable erionite fibers were detected in air samples collected from the affected villages, and lung tissue samples collected from mesothelioma cases contained erionite fibers. A higher proportion of ferruginous (iron-containing) bodies with a zeolite core were found in inhabitants of the contaminated villages than of those from the two control villages.[4][9][7] Erionite is reportedly present in the local volcanic tuff.[8] There is sufficient evidence of carcinogenicity of erionite in experimental animals. Rats exposed to erionite by inhalation or injection (intrapleural or intraperitoneal) and mice exposed by intraperitoneal injection had high incidences of mesotheliomas.[4][9]

Exposure

Deposits of fibrous erionite are located in Arizona, Nevada, Oregon, and Utah. These zeolite beds may be up to 15 feet thick and may lie in surface outcroppings. Erionite fibers have been detected in samples of road dust in Nevada and U.S. residents of the Intermountain West may be potentially exposed to fibrous erionite in ambient air.[4][10] In the summer of 2009 North Dakota began a study of possible erionite exposure among residents.[11] Erionite has also been identified in samples from the Tertiary Arikaree Formation in southeast Montana and northwest South Dakota.

Potential occupational exposure to erionite occurs during the production and mining of other zeolites. In the past, occupational exposure occurred from erionite mining and production operation. Erionite also was reported to be a minor component in some commercial zeolites.[12] Therefore, the use of other zeolites may result in potential exposure to erionite for the workers and the general population who use the zeolites in a variety of processes and products. Total dust exposures for miners in an open-pit zeolite mine that contained some erionite in Arizona ranged from 0.01 to 13.7 mg/m3; respirable dust in the mining area was 0.01 to 1.4 mg/m3.[4]

References

  1. ^ "General Erionite-Na Information". webmineral.com. http://webmineral.com/data/Erionite-Na.shtml. Retrieved 2009-07-13.  
  2. ^ "Erionite" (in NDhealth). North Dakota Department of Health. http://www.ndhealth.gov/EHS/erionite/. Retrieved 2009-07-13.  
  3. ^ "The Mineral Erionite". http://www.galleries.com/minerals/silicate/erionite/erionite.htm. Retrieved 2009-07-13.  
  4. ^ a b c d e IARC. 1987a. Silica and Some Silicates. IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans, vol. 42. Lyon, France: International Agency for Research on Cancer. 289 pp.
  5. ^ "IARC Monographs - Classifications - Group1" (in English). Overall Evaluations of Carcinogenicity to Humans.. IARC of the WHO. Last updated: 16 January 2009. http://monographs.iarc.fr/ENG/Classification/crthgr01.php. Retrieved 2009-07-21.  
  6. ^ Dikensoy O (July 2008). "Mesothelioma due to environmental exposure to erionite in Turkey". Current Opinion in Pulmonary Medicine 14 (4): 322–5. doi:10.1097/MCP.0b013e3282fcea65. PMID 18520266.  
  7. ^ a b Baris YI (1991). "Fibrous zeolite (erionite)-related diseases in Turkey". American Journal of Industrial Medicine 19 (3): 374–8. PMID 1848965.  
  8. ^ a b Baris YI, Grandjean P (March 2006). "Prospective study of mesothelioma mortality in Turkish villages with exposure to fibrous zeolite". Journal of the National Cancer Institute 98 (6): 414–7. doi:10.1093/jnci/djj106. PMID 16537834.  
  9. ^ a b IARC. 1987b. Overall Evaluations of Carcinogenicity. IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans, Supplement 7. Lyon, France: International Agency for Research on Cancer. 440 pp.
  10. ^ Rom, W. N., K. R. Casey, W. T. Parry, C. H. Mjaatvedt and F. Moatamed. 1983. Health implications of natural fibrous zeolites for the Intermountain West. Environ Res 30(1): 1-8.
  11. ^ "North Dakota Erionite Study Finally Underway". http://mesotheliomasos.com/news/north-dakota-erionite-study-finally-underway/. Retrieved 2009-07-13.  
  12. ^ Mondale, K. D., F. A. Mumpton and F. F. Aplan. 1978. Beneficiation of Natural Zeolites from Bowie, Arizona: A Preliminary Report. In Natural Zeolites: Occurrences, Properties, Uses. L. B. Sand and F. A. Mumpton, eds. New York: Pergamon Press. p. 527-537.

PD-icon.svg This article incorporates public domain material from websites or documents of the United States Government.[1]

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