Nontronite

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Nontronite
Specific gravity
2.3
Optical propertiesBiaxial (−)
Refractive indexnα = 1.530–1.580; nβ = 1.555–1.612; nγ = 1.560–1.615
Birefringenceδ = 0.030–0.035
References[2][3][4][5]

Nontronite is the iron(III) rich member of the

Al2O3 (ignited basis). Nontronite has very few economic deposits like montmorillonite.[6][7]
Like montmorillonite, nontronite can have variable amounts of adsorbed water associated with the interlayer surfaces and the exchange cations.

A typical structural formula for nontronite is

tetrahedral
sheet is composed mainly of silicon (Si4+), but can have substantial (about 1 in 8) substitution of either Fe3+ or Al3+, or combinations of these two cations. Thus, nontronite typically is characterised by having most (usually greater than 60%) of the layer charge located in the tetrahedral sheet. The layer charge is typically balanced by divalent calcium (Ca2+) or magnesium (Mg2+).

Nontronite forms from the

hydrothermal fluids and in deep sea hydrothermal vents.[9][10] Some evidence suggests that microorganisms may play an important role in their formation.[11] Microorganisms are also involved in reduction of structural iron in nontronite when soils undergo anoxia, and the reduced form of the clay appears to be highly reactive towards certain pollutants, perhaps contributing to the destruction of these compounds in the environment.[12][13]

The only known commercially viable and operational nontronite mine is located in

Canterbury, New Zealand. The mine is operated by Palmer Resources and the finished products are used internationally in industrial applications (pulp & paper, surface coating) and in cosmetics marketed as New Zealand Glacial Clay.[14]

See also

  • Saponite – Trioctahedral phyllosilicate mineral

References

  1. S2CID 235729616
    .
  2. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Nontronite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 28 July 2022.
  3. ^ Barthelmy, David (2014). "Nontronite Mineral Data". Webmineral.com. Retrieved 28 July 2022.
  4. ^ Nontronite, Mindat.org, retrieved 28 July 2022
  5. doi:10.1127/0935-1221/2006/0018-0753
    .
  6. ^ Eggleton, R. A. (1977), Clay minerals, vol. 12, pp. 181–194
  7. S2CID 129598259
    .
  8. S2CID 95954306
    .
  9. ^ Bischoff (1972), Clays and Clay Minerals, vol. 20, pp. 217–223
  10. ^ Eggleton, R. A. (1975). "Nontronite topotaxial after hedenbergite". American Mineralogist. 60: 1063–1068.
  11. ^ Kohler; et al. (1994), Clays and Clay Minerals, vol. 42, pp. 680–701
  12. ^ Tor, J., C. Xu, J. M. Stucki, M. Wander, G. K. Sims (2000). "Trifluralin degradation under micro-biologically induced nitrate and Fe(III) reducing conditions". Env. Sci. Tech. 34: 3148–3152.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. ^ Xu, J., J. W. Stucki, J. Wu, J. Kostka, and G. K. Sims (2001). "Fate of atrazine and alachlor in redox-treated ferruginous smectite". Env. Tox. & Chem. 20: 2717–2724.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  14. ^ "New Zealand Glacial Clay Fact Sheet". Palmer Resources Limited.
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