Nontronite


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Related to Nontronite: saponite, Palygorskite

nontronite

[′nän·trə‚nīt]
(mineralogy)
Na(Al,Fe,Si)O10(OH)2 An iron-rich clay mineral of the montmorillonite group that represents the end member in which the replacement of aluminum by ferric ion is essentially complete. Also known as chloropal; gramenite; morencite; pinguite.

Nontronite

 

a mineral of the montmorillonite-vermiculite group. In terms of its crystallochemical structure, nontronite is a phyllosilicate. Its chemical composition is

Fe23+ [AlxSi4-xO10](OH)2 · Na0.33(H2O)4

It contains significant quantities of Al2 OO3 (up to 14 percent) and MgO (up to 8 percent), as well as small quantities of CaO (up to 2 percent), K2O, Na2O, and sometimes NiO and Cr2O3. The basis of the structure of nontronite is a three-layer unit of the talc or pyrophyllite type—two layers of SiO tetrahedrons separated by an octahedral layer of FeO6; between the unit layers are molecules of water with exchange bases of Na. Al replaces the Si in the tetrahedrons.

Nontronite is an isomorphic mixture of nontronite proper and montmorillonite. It crystallizes in the monoclinic system. Aggregates of nontronite are usually compact, claylike, and crypto-crystalline, less frequently in the form of pseudomorphs after dark-colored minerals. Their color ranges from greenish yellow to dark green. Their hardness on Mohs’ scale is about 2, and their density is up to 2,100 kg/m3. Nontronite is a typical super-gene mineral, which forms primarily upon the weathering of iron-bearing silicates of various ultrabasic igneous and meta-morphic rocks. Nontronite masses rich in nickel are economically important.

M. D. DORFMAN

References in periodicals archive ?
Another clay mineral commonly recorded in the low temperature hydrothermal alteration of basalts is nontronite, which has been described in the literature as genetically related to bacteria in marine white smoker chimneys from the Galapagos Spreading Center and Mariana Trough by Kohler et al.
Control of Fe(III) Site Occupancy on the Rate and Extent of Microbial Reduction of Fe(III) in Nontronite.
The vesicles and fractures in basalts were gradually filled up with secondary minerals, developing amygdales and veins usually showing mineral zoning distribution though, in some cases, they were not completely filled Figure 5a gives an example of the occurrence of a mixed layer of celadonite (Fe-rich mica) and non-tronite (Fe-rich smectite) and vesicles commonly lined by these mineral phases Celadonite is usually green and botroidal and has fibrous spheroidal morphology, having detectable striated birefringence under crossed nicols Nontronite is typically brown in transmitted light and does not have a discernable structure except for banding parallel to the cavity wall It occasionally exhibits geopetal features.
Model 3 has allowed identification of minerals of the kaolin-serpentine group (kaolinite, dickite and halloysite), Model 4 has allowed identification of minerals of the smectite group (Na-montmorillonite, Ca-montmorillonite, nontronite and hectorite) and Model 5 has allowed identification of micas (biotite, muscovite) and illite.
However, under a stronger or longer interaction, the neoformation of trioctahedral smectites such as saponite-stevensite, Fe(II)-rich saponite or dioctahedral nontronite (as a function of the Mg and Fe(II)/Fe(III) activities in the environment, respectively), corrensite and Fe-Mg-rich chlorite may occur as recorded in some active geothermal and diagenetic systems (Yamada and Nakasawa, 1993; Beaufort et al.
Nontronite occurs as soft, light yellow to greenish aggregates formed, in part, from iron derived from oxidation of pyrite near the surface and redeposited below.
Associated minerals are: microcline, aegirine, arfvedsonite, nepheline, eudialyte, albite, lorenzenite, loparite, aenigmatite, manganneptunite, murmanite, analcime, natrolite, stilbite, chabazite, kuzmenkoite-Mn, nontronite, and others.
Associated minerals are: muscovite, caysichite-(Y), donnayite-(Y), kamphaugite-(Y), malachite, nontronite, "limonite" pseudomorphs after pyrite, calcite and gypsum.
2001, In situ atomic force microscopy study of hectorite and nontronite dissolution: Implications for phyllosilicate edge surface structures and dissolution mechanisms.
Mineralogists of the 19th century were much more successful in the description of new layer hydrosilicates: allophane, amesite, antigorite, aspidolite, batavite, biotite /a series name/, celadonite, chamosite, chrysotile /a series name/, clinochlore, corundophyllite, cronstedtite, delessite, diabantite, ephesite, glauconite /a series name/, halloysite, kaolinite, muscovite, nacrite /a polytype/, nontronite, palygorskite, paragonite, penninite /or pennine/, phengite /a series name/, phlogopite, polylithionite, pyrophyllite, ripidolite, roscoelite, saponite, sauconite, sepiolite, serpentine, siderophyllite, stevensite, tainiolite, thuringite, vermiculite /trioctahedral and dioctahedral, distinguished in the 20th century/, volkonskoite, zinnwaldite /a series name/.
A search through the recently computerized X-ray film archive (9-cm Debye-Scherrer camera) at the Mineralogical-Geological Museum in Oslo verifies that antigorite, clinozoisite, hematite, hornblende, hydrozincite, lollingite, nontronite, orthochrysotile, portlandite, and stevensite have also been identified from mines and prospects in the Kongsberg area.