Tubular and spheroidal halloysite in pyroclastic deposits in the area of the Roccamonfina volcano (Southern Italy)

Adamo, Paola; Violante, P.; Wilson, M. J.

doi:10.1016/s0016-7061(00)00076-8

Cited by 57 publications

(47 citation statements)

References 13 publications

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“…However, EDX analyses of discrete halloysite particles shows that the molar ratios of SiO 2 /Al 2 O 3 and SiO 2 /Al 2 O 3 + Fe 2 O 3 were lower for spheroidal halloysites. Similar molar ratios for tubular and spheroidal morphology halloysite have been reported previously by Adamo et al (2001) in the weathered ash fall deposits of the Roccamonfina volcanic area (southern Italy). We suggested that the different morphological forms of halloysite result from conditions of growth in different microenvironments: tubular halloysite occurred in the free spaces, in contrast to the more compact vitreous starting material, in which the spheroidal form is found.…”

Section: Discussionsupporting

confidence: 87%

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Mineralogical and geochemical studies of hardened subsurface layers in soils of the Azufres and Atecuaro volcanic calderas, southwestern Mexico

Ostrooumov¹,

Monroy²,

Servenay³

2005

Can. J. Soil. Sci.

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Ostrooumov, M., Monroy, V. H. G. and Servenay, A. 2005. Mineralogical and geochemical studies of hardened subsurface layers in soils of the Azufres and Atecuaro volcanic calderas, southwestern Mexico. Can. J. Soil Sci. 85: 611-624. Free silica and halloysite-bearing hardened subsurface layers in the ash fall deposits of the Azufres and Atecuaro volcanic calderas (Michoacan State, southwestern Mexico), known as "tepetates", have been characterized by chemical analysis, X-ray diffraction (XRD), Raman and Infrared spectrometry, optical (OM) and scanning (SEM) microscopy with energy dispersive X-ray analysis (EDXRA). Chemical analysis of these weathered and hardened formations shows the oxidation of Fe 2+ , enrichment of Al, Fe 3+ and Ti, loss of Si, Na, Ca, K, Mg, and formation of minerals with hydroxyls groups. Tepetates are characterized by elevated SiO 2 /Al 2 O 3 molar ratios (4. 86-8.82) that show part of the SiO 2 has crystallized in free siliceous phases. X-ray analysis reveals hydrated (1.0 nm) and dehydrated halloysite (0.7 nm), sanidine, plagioclases, cristobalite, and tridymite. Raman and infrared spectra confirm the presence of these mineral phases and show that the structural transformations occur in opal neoformations. SEM shows a compact matrix with a skeleton of different phenocrysts (aluminosilicates, ferromagnesian minerals and various crystalline silica phases) and the presence of non-crystalline silica (volcanic glass and opal with different degrees of crystallinity). The tepetates form by interaction of two processes: volcanic ash fall then subsequent weathering under variable climatic conditions. These indurated horizons are partly or totally cemented by the diagenetic secondary minerals: non-crystalline silica with variable crystal chemical characteristics and clay minerals. . Ils ont pour cela recouru à l'analyse chimique, à la diffraction par rayons X, à la spectrométrie Raman et à infrarouge, à la microscopie photonique et par balayage (MB) ainsi qu'à l'analyse radiologique par dispersion d'énergie. L'analyse chimique de ces formations durcies et altérées révèle l'oxydation du Fe 2+ , un apport d'Al, de Fe 3+ et de Ti, la perte de Si, Na, Ca, K et Mg, et la formation de minéraux à groupes hydroxyles. Les tepetates se caractérisent par un ratio molaire élevé de SiO 2 /Al 2 O 3 (4,86 à 8,82), signe qu'une partie du SiO 2 s'est cristallisée dans la silice libre. L'analyse radiologique révèle de l'halloysite hydratée (1,0 nm) et déshydratée (0,7 nm), de la sanidine, des plagioclases, de la cristobalite et de la tridymite. L'analyse par spectrométrie Raman et infrarouge confirme la présence de ces phases minérales et montre que les transformations structurales surviennent dans les néoformations d'opales. La MB montre une matrice compacte ayant pour squelette différents phénocristaux (aluminosilicates, minéraux ferro-magnésiens et diverses phases de silice cristalline) ainsi que la présence de silice non cristalline (verre volcanique et opales à cristallinité variable). Les tepetates naissent ...

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Section: Discussionsupporting

confidence: 87%

“…In addition, dehydrated halloysite has a spheroidal morphology while hydrated halloysite is normally tubular. Both tubular and spheroidal crystals of halloysite were also described in the weathered pyroclastic deposits in Southern Italy (Adamo et al 2001).…”

Section: Scanning Electron Microscopymentioning

confidence: 89%

Mineralogical and geochemical studies of hardened subsurface layers in soils of the Azufres and Atecuaro volcanic calderas, southwestern Mexico

Ostrooumov¹,

Monroy²,

Servenay³

2005

Can. J. Soil. Sci.

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“…Many typical vibration bands can be found on IR spectra of different clay minerals, while the spectra of halloysite in the range 550~1350 cm −1 are similar to kaolinite [53], so the ascriptions are often difficult to be recognized, but they still have some distinctive bands. Each vibration line is assigned to the stretching or deformation of the groups and bonds in the samples according to the literature [48,[54][55][56][57]; the FTIR spectra of Hal from different regions are shown in Figure 2 and the ascriptions are included in Table 2, respectively. The double adsorption bands at around 3696 cm −1 and 3620 cm −1 were ascribed to the stretching vibration of the adsorbed water.…”

Section: Ftir Analysismentioning

confidence: 99%

Mineralogy and Physico-Chemical Data of Two Newly Discovered Halloysite in China and Their Contrasts with Some Typical Minerals

Ouyang

Zhang

et al. 2018

Minerals

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Abstract:We report in this article the systematical acquisition of physico-chemical parameters for two newly discovered halloysite (Hal) minerals from Shiyan and Tongling in China. As the comparative reference, the data from Hal in Linfen, Chenxi, and the salt lake in Australia (samples were abbreviated as Hal-AU, Hal-SY, Hal-LF, Hal-CX and Hal-TL, respectively) were also investigated using X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FTIR), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray fluorescence, surface zeta potential measurements and N 2 adsorption-desorption isotherms. The newly found minerals were probably formed in hydrothermal leaching and sedimentary circumstances. The Hal-SY contains 7 Å-halloysite and dickite, while Hal-TL contains 10 Å-halloysite with some alunite (similar with Hal-CX). Other impurities found in the samples include quartz, gibbsite, iron oxide and anatase. All of them showed tubular morphology with diameter in the range of 30-90 nm and a length of 300-2500 nm, while the Hal-SY has the largest inner diameter to about 150 nm. Specific surface areas varied from 26.0~59.0 m 2 ·g −1 . In addition, maximum CEC (cation exchange capacity) of the newly found Hal was about 40 cmol/kg, while that of Hal-AU was relatively low (8 cmol/kg) due to the sedimentary nature of Salt Lake circumstances. The surface charge was predominantly negative over most of the relevant pH range (>2.0). It can be concluded that the different morphology and impurity content of halloysite will greatly affect the surface area, pore volume, and cationic exchange capacity (CEC) of the minerals.

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“…Nagasawa and Moro (1987); Tazaki (1982); ; Singer et al (2004) noticed that spheroidal forms have higher Fe content than tubular ones. Such trend is not found in other cases such as those studied by Soma et al (1992), Adamo et al (2001). Even a biogenic origin was proposed by Tazaki and Asada (2003), who observed that a spheroidal halloysite is formed by bacterial activities in freshwater and natural sediment systems at room temperature.…”

Section: Resultsmentioning

confidence: 76%

“…Nagasawa (1978); Tomura et al (1985); Quantin et al (1988), Bailey (1989), Adamo et al (2001); Singer et al (2004); Churchman and Lowe (2012) considered that spheroidal halloysite comes from a fast dissolution of volcanic glass that results in a supersaturated solution which favors the formation of this particular shape. Also, it can be texturally constrained as in pumice cavities (Adamo et al, 2001). The origin of spheroidal halloysite from the transformation of allophane has been proposed by different authors.…”

Section: Resultsmentioning

confidence: 99%

Spheroidal halloysites from Patagonia, Argentina: Some aspects of their formation and applications

Cravero

Fernández

Marfil

et al. 2016

Applied Clay Science

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Halloysite deposits in Argentina have been identified in the province of Río Negro (Patagonia). The mineralized area occurs as altered zones in Eocene volcanic-pyroclastic rocks, dacitic to rhyolitic in composition. A comprehensive study of these deposits was carried out by means of mineralogical, geochemical and isotopic analyses. Intense weathering has transformed the whole rock to a white mass composed of 75% -90% halloysite + kaolinite, with cristobalite, tridymite, and quartz, as the main non-clay minerals. Ferruginous beidellite and titanium minerals are also present in minor amounts. The halloysite-kaolinite ratio ranges from 75 to 25 to 100-0. Due to the alteration of very dense rocks, halloysite morphology is predominantly spheroidal. Tubular halloysite is the main constituent in more porous rocks, but the latter are scarce in the area. Because of the predominance of the spheroidal type, the use of halloysite as HNT (halloysite nanotube) is not feasible. Nonetheless, this mineral can be modified by different organic molecules, and used to remove pollutants such as emulsified hydrocarbons and heavy metals. A special product made with this halloysite is used as sunscreen when sprayed on fruits in areas of intense solar radiation. The whiteness of this mineral is not very high due to the amount of titanium oxide present in its composition (about 1%). Nevertheless, titanium oxide is present as individual particles, so it could be removed by a mechanical process. New applications for spheroidal halloysite are currently being investigated. Moreover, depending on the price and demand, the tubular halloysite of low grade deposits could be exploited.

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Tubular and spheroidal halloysite in pyroclastic deposits in the area of the Roccamonfina volcano (Southern Italy)

Cited by 57 publications

References 13 publications

Mineralogical and geochemical studies of hardened subsurface layers in soils of the Azufres and Atecuaro volcanic calderas, southwestern Mexico

Mineralogical and geochemical studies of hardened subsurface layers in soils of the Azufres and Atecuaro volcanic calderas, southwestern Mexico

Mineralogy and Physico-Chemical Data of Two Newly Discovered Halloysite in China and Their Contrasts with Some Typical Minerals

Spheroidal halloysites from Patagonia, Argentina: Some aspects of their formation and applications

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