Misplaced Pages

Nontronite

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Phyllosilicate mineral
Nontronite
Nontronite from Slovakia
General
CategoryPhyllosilicates
Smectite group
Formula
(repeating unit)		(CaO0.5,Na)0.3Fe2(Si,Al)4O10(OH)2·nH2O
IMA symbolNon
Strunz classification9.EC.40
Crystal systemMonoclinic
Space groupC2/m (no. 12)
Identification
ColorYellow, olive-green, green, orange, brown
Crystal habitEarthy masses
CleavagePerfect basal
Fractureuneven
Mohs scale hardness1.5 to 2
LusterEarthy to dull
StreakColorless
Specific gravity2.3
Optical propertiesBiaxial (−)
Refractive indexnα = 1.530–1.580; nβ = 1.555–1.612; nγ = 1.560–1.615
Birefringenceδ = 0.030–0.035
References

Nontronite is the iron(III) rich member of the smectite group of clay minerals. Nontronites typically have a chemical composition consisting of more than ~30% Fe2O3 and less than ~12% Al2O3 (ignited basis). Nontronite has very few economic deposits like montmorillonite. 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 Ca.5(Si7Al.8Fe.2)(Fe3.5Al.4Mg.1)O20(OH)4. The dioctahedral sheet of nontronite is composed mainly of trivalent iron (Fe) cations, although some substitution by trivalent aluminium (Al) and divalent magnesium (Mg) does occur. The tetrahedral sheet is composed mainly of silicon (Si), but can have substantial (about 1 in 8) substitution of either Fe or Al, 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 (Ca) or magnesium (Mg).

Nontronite forms from the weathering of biotite and basalts, precipitation of iron and silicon rich hydrothermal fluids and in deep sea hydrothermal vents. Some evidence suggests that microorganisms may play an important role in their formation. 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.

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.

See also

  • Saponite – Trioctahedral phyllosilicate mineral

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. 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. Dainyak, Lidia G.; Zviagina, Bella B.; Rusakov, Viacheslav S.; Drits, Victor A. (2006). "Interpretation of the nontronite-dehydroxylate Mossbauer spectrum using EFG calculations". European Journal of Mineralogy. 18 (6): 753–764. Bibcode:2006EJMin..18..753D. doi:10.1127/0935-1221/2006/0018-0753.
  6. Eggleton, R. A. (1977), Clay minerals, vol. 12, pp. 181–194
  7. Keeling; et al. (2000). "Geology and Characterization of Two Hydrothermal Nontronites from Weathered Metamorphic Rocks at the Uley Graphite Mine, South Australia". Clays and Clay Minerals. 48 (5): 537–548. Bibcode:2000CCM....48..537K. doi:10.1346/CCMN.2000.0480506. S2CID 129598259.
  8. Gates; et al. (2002). "Mountainville nontronite". Clays and Clay Minerals. 50: 223–239. doi:10.1346/000986002760832829. 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.
Phyllosilicates
Micas
Talcs
Pyrophyllite series
Kaolinites
Serpentines
Corrensites
Smectites and vermiculite family
Chlorites
Allophanes
Sepiolites
Pyrosmalites
Stilpnomelanes
  • Structural groups mainly; based on rruff.info/ima, modified
  • Minerals portal
Clay minerals
Minerals portal
Stub icon

This article about a specific mineral or mineraloid is a stub. You can help Misplaced Pages by expanding it.

Categories: