Halloysite Tubes Research Articles

Intercalation and polymerisation of aniline within a tubular aluminosilicate

The intercalation and polymerization of aniline within the pores of a natural tubular Cu2+-exchanged aluminosilicate clay known as halloysite is studied. The mesoscopic clay fibres have internal diameters of approximately 180 Å and lengths of up to 20 µm and can be deposited as films into which aniline is introduced from the vapour phase. The aniline composite was characterized by powder XRD, TGA, EPR, UV-Vis, XPS and IR spectroscopy. The present results confirm the presence of polyaniline on the internal and external surfaces of the halloysite tubes, thus indicating that the composite material could act as a molecular wire. The polyaniline initially sorbed onto the external surfaces is in a reduced state and evolves toward a more oxidized state as the duration of exposure of the film to aniline vapour increases.

FT-IR Partial Least-Squares Analysis of Tubular Halloysite in Kaolin Samples from the Mount Hope Kaolin Deposit

AbstractA method of infrared (IR) analysis for quantitative determination of tubular halloysite in mixtures with kaolinite was investigated for drill hole samples collected during an assessment of paper-coating kaolin resources at the Mount Hope Kaolin Deposit, Eyre Peninsula, South Australia. Tubular, dehydrated halloysite from the deposit does not readily intercalate formamide, and the proportion of tubes in <2 μm size-fractions was determined initially from scanning electron micrographs. For samples showing a range of tube contents, a strong correlation between IR spectral response and counts of halloysite tubes was established using partial leastsquares analysis. This provided a rapid technique suitable for routine determination of tubular halloysite in samples from the Mount Hope deposit. Although the universality of the method remains to be tested, it offers an alternative approach to other analytical techniques for assessment of kaolin deposits where the presence of halloysite is suspected.

Boxwork Fabric of Halloysite-Rich Kaolin Formed by Weathering of Anorthosite in the Sancheong Area, Korea

AbstractBoxwork fabric in which numerous thin or thick halloysite walls are interconnected into a microscopically porous cellular pattern is widely developed in the halloysite-rich kaolin formed by weathering of anorthosite in Sancheong, Korea. Studies using optical microscopy, scanning electron microscopy, and transmission electron microscopy have been carried out in order to elucidate the detailed features and origin of the boxwork.In the early stage of weathering, halloysite spheres formed in etch pits on the walls of microstructural discontinuities in the slightly weathered rock. With further weathering, the halloysite spheres grew to discs or flattened globules, which in turn coalesced to form large planar halloysite plates amid narrow fissures. The halloysite plates were detached by dissolution of the plagioclase in groundwater. Continued growth of the halloysite tubes in the plates resulted in the wrinkling of the plates. Finally, the plagioclase was completely dissolved by groundwater, leaving the boxwork of wrinkled halloysite walls and large pores. The relatively high rigidity of the boxwork is due to the compact agglomeration of halloysite tubes within the wrinkled halloysite walls.Cation balance calculation shows that Al was significantly mobilized during the formation of the boxwork in the weathering environment. The well-developed microfissures, the high dissolution rate of the calcic plagioclase, and the rapid flow of groundwater in a mountainous topography with relatively steep (20°) slope have been the factors controlling the formation of the porous boxwork in the halloysite-rich kaolin of the Sancheong area.

An Electron Optical Investigation of the Alteration of Kaolinite to Halloysite

AbstractParallel-oriented and exceptionally long (> 10 μm) tubes of halloysite occur in the pallid zone of a deeply-weathered lateritic profile on granite in southwest Australia.Transmission electron microscopy and selected-area electron diffraction of ultrathin sections showed that kaolinite plates within pseudomorphs of mica crystals had fractured at irregular intervals along the a crystallographic axis to produce laths elongated along the b axis. The laths near the edges of the pseudomorphs were less constrained by the pseudomorph and had rolled to produce halloysite tubes. The tubes varied in diameter and degree of roundness. Some tubes were polyhedral rather than cylindrical in cross section. The length and number of planar faces in a tube and the angle between faces varied, exhibiting no consistent pattern.Tubes in dispersed clay samples showed two types of twinning. In the first type, tubes and associated laths were joined together side by side. In the second type, single tubes bifurcated into two individual tubes. It is proposed that the first type of twinning occurred by folding of adjacent laths that remained joined together while the second type occurred due to exfoliation of a thick lath followed by folding of the exfoliated lath fragments into tubes.Analytical electron microscopy showed that the chemical compositions of halloysite tubes, laths, and kaolinite plates were similar with the average cation exchange capacity of single tubes being small (4.5 meq/100 g) but higher than values for laths (2.8 meq/100 g) and plates (1.9 meq/100 g).

Laumontite in Soils of the San Gabriel Mountains, California

AbstractLaumontite, a Ca‐rich zeolite, is widespread and locally abundant in the San Gabriel Mountains of southern California. It occurs in hydrothermally altered rocks of various origins and is inherited by the overlying soils. The objectives of this study were to determine the distribution and properties of laumontite in these soils. Laumontite was found in soils derived from anorthosite, arkosic sandstone, and granodiorite. All of the soils were Entisols, composed largely of colluvium, on steep, chaparral‐covered slopes. Soil depths ranged from 16 to 32 cm over 25 to 40 cm of saprolite (Cr horizon). Soil pH ranged from 5.0 in the A horizon of the soil on sandstone to 7.2 in the Cr horizon of the anorthosite‐derived soil. Laumontite was found in sand, silt, and clay fractions of the soils. Its particle‐size distribution in the soil depended on its grain size in the parent rock and its weathering within the soil. Comparisons of laumontite grain morphology using scanning electron microscopy showed grains in the A horizons to be rounded, dissolution pitted, and crusted with weathering products, whereas those in the Cr horizons tended to have more angular, fresher crystal faces. Halloysite tubes have formed on some laumontite grain surfaces. Although the low Si/Al ratio of laumontite indicates a high cation‐exchange capacity, only 17 cmolc kg−1 of native cations were extracted by shaking in 1 M NaCl solution for 17 d. Fewer cations were displaced by Ba, Sr, Cs, and NH4. Apparently, diffusion of cations from the one‐dimensional channels of laumontite is very slow. Laumontite does not contribute significantly to the cation‐exchange capacity of these soils, which also contain smectite and vermiculite.

Observation of the Hydrated form of Tubular Halloysite by An Electron Microscope Equipped with An Environmental Cell

AbstractThe hydrated form of tubular halloysite [halloysite (10 Å)] was observed by a conventional electron microscope equipped with an environmental cell (E.C.), by which the “natural” form was revealed without dehydration of the interlayer water. This study mainly reports the selected area electron diffraction (SAED) analysis of the halloysite (10 Å) and its morphological changes by dehydration. The SAED pattern showed halloysite (10 Å) has two-layer periodicity in a monoclinic structure with the unit cell parameters of a = 5.14 Å, b = 8.90 Å, c = 20.7 Å, β = 99.7°, in space group Cc, and almost the same structure as the dehydrated form of halloysite [halloysite (7 Å)]. This means that the dehydration of the interlayer water did not greatly change or affect the structure of halloysite (10 Å). Accompanying the dehydration of the interlayer water, there appeared along the halloysite tube axis clear stripes that were about 50–100 Å in width. The diameters of the tubular particles also increased about 10%. From the results of various experiments, such as a focussing series, observation of the surface structure by the replica method, observation of end-views of the tubular particles, and others, these two phenomena were explained as follows: Halloysite crystals have “domains” along the c-axis direction, the thicknesses of the “domains” vary ca. 50–100 Å. They are tightly connected with each other when the halloysite is hydrated, but are separated from each other by the dehydration of the interlayer water, whereupon the stripes come into existence along the tube axis. Taking these considerations into account, a model of dehydration is proposed. Moreover, a new method of calculating the β-angle is proposed in the Appendix.

The Formation of Halloysite Tubes from Spherulitic Halloysite

The Formation of Halloysite Tubes from Spherulitic Halloysite

Internal and External Morphology of Tubular and Spheroidal Halloysite Particles

AbstractTubular halloysite from Wagon Wheel Gap, Colorado and spheroidal halloysite from Redwood County, Minnesota were examined by transmission electron microscopy. Clay samples were prepared by the following techniques: drop-mounted suspension on carbon support films; thin sections of clay in Araldite epoxy resin; and carbon-platinum-palladium single-stage replicas.Both types of dehydrated halloysite have interlayer separations between packets of layers. Halloysite tubes are composed of packets as thin as five layers which sometimes reveal a rolled interior configuration in cross-sectional view. Thicker tubes are composed of many layers per packet. Some large tubes appear in cross section as folded packets of layers. The interior morphology of spheroidal halloysite particles is more irregular and the layer structure is more discontinuous than in most tubes. The spheroidal halloysite of this study is characterized by external tangential plates with hexagonal shape suggestive of kaolinite.

Clay Mineral Formation in Sea Water by Submarine Weathering of K-Feldspar

AbstractA suite of granodiorite samples was collected by dredging from depths of about 1000 m from the walls of Carmel and Monterey submarine canyons, Monterey Bay, California. One surface of each of the various granodiorite slabs was weathered and encrusted with marine organisms. The weathering is maximum at the surface and penetrates to a depth of about 20 cm and selectively alters the feldspars to clay. Potassium feldspars are most severely altered. Mineral selective attack, shallow depth of weathering, restriction of biological growth to weathered surfaces, and regional geological setting are interpreted to mean that the samples were broken from bedrock and that this granodiorite probably weathered in the marine environment.Authigenic clays formed as a result of the submarine weathering of the granodiorite are kaolinite, K-mica, montmorillonite, and halloysite.These data suggest that the assemblage K-mica, montmorillonite, and kaolinite have a phase join that may lie on or close to the composition of sea water. Furthermore, kaolinite may be unstable in sea water and gradually break up to form halloysite tubes. The possible influence of biologie agents is suggested in the formation of marine halloysite.

Halloysite and Gibbsite Formation in Hawaii

AbstractDesilication and removal of bases from the basalitic rocks of the Hawaiian Islands produces large amounts of halloysite and gibbsite, together with variable quantities of allophane and nontronite, iron and titanium oxides, and amorphous mineral and gel material.The nature and relative abundance of intermediate and end products of weathering depend primarily upon the amount of rainfall, angle of slope, and texture of the rock. The formation of clay minerals is the common step in the transformation of primary silicates to oxides and hydroxides, but the amount and relative importance of the clay “stage” depend on the intensity of the weathering process.Halloysite forms from plagioclase usually by alteration of first the core and subsequently the rim of the feldspar laths. No kaolinite was observed, its absence being attributed to the absence of fine-grained mica as an intermediate weathering product.Gibbsite is produced by (1) removal of silica from halloysite, (2) dehydration of Al-gel, and (3) precipitation from solution. Although it is possible that the mineral may form directly from feldspar, halloysite is the common crystalline intermediate on both the megascopie and microscopic scales.An amorphous transition state, probably ranging in composition from allophane to Al-gel, exists as part of the change from halloysite to gibbsite as evidenced by electron microscope and diffraction work on pseudomorphs after halloysite tubes found in certain samples studied in more detail than others.Volcanic glass is the apparent source of most Al-Fe-Si gel material which upon dehydration becomes allophane, cliachite, or gibbsite depending on the kind and relative proportion of the cations present.

The Scattering of Tubular Objects

The scattering intensity due to tubular objects as exemplified by certain halloysites is discussed. The intensity function is characterized by the presence of bands with a steep inside front and long trailing tails. The intensities of these bands are largely determined by the “unit cell” of the curved sheets which make up the tube, while the positions of the edges of the bands are characteristic of dimensions and type of unit cell. The region of reciprocal space close to the Z-axis (chosen parallel to the axis of the tube) contains information about the over-all structure of the tube. An electron diffraction photograph of a single halloysite tube (Taggart, Milligan and Studer, presented at the Third National Clay Conference) illustrates these features. Additional equatorial reflections indicate that the curved sheet has in turn a layer structure, the layers in effect having random displacement to each other.