Dietary clay supplements (bentonite and kaolinite) have been used as binding and lubricating agents in the production of pelleted feeds for chickens. The high-swelling and water absorbing capacity of some bentonites make them attractive dietrary additives for control of wet droppings in caged layers. In addition, experiments show that layers fed on these diets exhibit significant increases in body weight, egg size, and life expectancy even though their total caloric intake is less than that of the control group. Dietary kaolin improves caloric efficiency even more than bentonite but without apparent effect upon growth or carcass quality. Kaolins of smaller particle size are superior to those of larger size in improving caloric efficiency. The effective kaolins are estimated to be worth approximately two calories of metabolizable energy per gram. The major beneficial effect appears to be due to a slowing down of the rate of feed passage through the intestinal tract. Possible uptake of trace elements required for optimum nutrition has not yet been evaluated.

Flint clay is defined as a sedimentary, microcrystalline to crystalline clay (rock) composed dominantly of kaolin, which breaks with a pronounced conchoidal fracture and resists slaking in water. Additional ceramic (refractory) properties are implied, but not expressed, in the definition. Flint clay first given recognition in the U.S.A., has been observed on all continents; it will probably be found to be more abundant than its occurrences reported to date. It occurs in rocks mainly Carboniferous or Cretaceous in age, and is invariably associated with plant- or coal-bearing measures.

The environment of deposition is commonly lowlying paludal, in basins in either clastic silicate rocks or in karstic carbonates. It is inferred that parent illitic and/or kaolinitic clay colloids were transported into the swamps and there under-went further dialysis, alteration, and eventual crystallization in situ, producing a notably homogeneous kaolinite clay possessing interlocking crystallinity. Some occurrences were further desilicated to high-alumina minerals, particularly to diaspore and boehmite.

Flint clay is interpreted as being an intermediate member of a so-called flint-clay facies which is a claystone sequence ranging from high-alumina minerals (or potentially so) formed on the highest part, structurally and/or topographically, of the depositional area, and grading down-structure and/or lower in elevation through flint clay to iliite-kaolinite plastic clay and thence to marine illitic shale, all being equivalent stratigraphically. The geochemical reactions are depotassification of parent clay by substitution of K+ by H+, and desilication, especially where high-alumina minerals are formed.

The morphology of synthetic montmorillonite and hectorite was studied using electron microscopy and X-ray diffraction techniques. Interstratified montmorillonite-mica particles may be identified in these specimens by electron microscopy and electron diffraction techniques. Magnesium-substituted samples were found to exhibit an increasing amount of curling with increasing magnesium content except for the end-member magnesium clay. Synthetic hectorite clays do not necessarily have the same morphology as natural hectorite clays. A study was made also of the morphology of a series of samples obtained from a study of kinetics of crystallization. Boehmite and montmorillonite were the basic components of the system. It was found that the montmorillonite clay particles curled around the boehmite which had been adsorbed on the basal surfaces on the montmorillonite.

Montmorillonite was found to be the dominant clay mineral in surface horizons of certain soils of the North Carolina Coastal Plain whereas a 2:1–2:2 intergrade clay mineral was dominant in subjacent horizons. In all soils where this clay mineral sequence was found, the surface horizon was low in pH (below 4·5) and high in organic matter content. In contrast, data from studies of other soils of this region (Weed and Nelson, 1962) show that: (1) montmorillonite occurs infrequently; (2) maximum accumulation of the 2:1–2:2 intergrade normally occurs in the surface horizon and decreases with depth in the profile; (3) organic matter contents are low; and (4) pH values are only moderately acid (pH 5–6).

It is theorized that the montmorillonite in the surface horizon of the soils studied originated by pedogenic weathering of the 2:1–2:2 intergrade clay mineral. The combined effects of low pH (below 4·5) and high organic matter content in surface horizons are believed to be the agents responsible for this mineral transformation. The protonation and solubilization (reverse of hydrolysis) of Al-polymers in the interlayer of expansible clay minerals will occur at or below pH 4·5 depending on the charge and steric effects of the interlayer. A low pH alone may cause this solubilization and thus mineral transformation, but in the soils studied the organic matter is believed to facilitate and accelerage the transformation. The intermediates of organic matter decomposition provide an acid environment, a source of protons, and a source of watersoluble mobile organic substances (principally fulvic acids) which have the ability to complex the solubilized aluminum and move it down the profile. This continuous removal of solubilized aluminum would provide for a favorable gradient for aluminum solubilization.

The drainage class or position in a catena is believed to be less important than the chemical factors in formation of montmorillonite from 2:1–2:2 intergrade, because montmorillonite is present in all drainage classes if the surface horizon is low in pH and high in organic matter.

Geothermal fluid discharged by steam wells, which have been core drilled to depths as much as 4500 ft at Wairakei, New Zealand, has altered Pliocene to Pleistocene, silicic, mainly glassy volcanics and related aqueous tuffs and breccias. Measured temperatures (max. 265°C) indicate epithermal to mesothermal conditions in buried fault fissures, the locus of both the hydrothermal fluid and most intense alteration.

A supergene kaolinite alteration zone is distinguished from hypogene Ca-montmorillonite and combined micaceous and chloritic zones. The hypogene zones are usually wide and are temperature dependent and localized along fault fissures. Other common hypogene minerals are alkali feldspars, wairakite, epidote, quartz, calcite, laumontite, ptilolite, pyrite and pyrrhotite. Prehnite is rare.

The micaceous clay minerals include illite (about 10 Å) and a series of random mixed-layer illite-montmorillonites with d(001) values ranging from 10·28 to 12·45 Å. The amount of interstratified montmorillonite is related to temperature and fault fissures. Apart from rare mixed-layer swelling chlorite, the Fe-rich chloritic clay shows little or no variation in its composition. Both the micaceous clays and the chloritic clay result from alteration of earlier formed Ca-montmorillonite.

The stability of hydrothermal minerals is controlled by the temperature and chemical composition of the geothermal fluid ascending along the fault fissures. K-feldspar but not albite is deposited on fissure walls, but both alkali feldspars replace primary soda-lime plagioclase in the wall rock. The absence of albite on fissure walls is ascribed to low aqueous mNa+/mK+ ratio. Primary quartz is not affected by the altering solution but hydrothermal quartz is deposited on fissure walls and in the wall rock.

A theory for the quantitative analysis of multicomponent mineral systems by means of X-ray diffraction is presented. A linear interaction between mineral pairs is postulated. The theory is verified experimentally for bicomponent and tricomponent systems using a variety of sample preparation techniques including random powder mounts, suspensions sedimented onto glass slides, and pressed powder pellets. The minerals studied include quartz, fluorite, kaolinite, glauconite, illite, and montmorillonite.

The determination of the linear interaction factors for mineral pairs is treated theoretically and experimentally. Emphasis is placed upon techniques that are applicable to naturally occurring mineral systems. Four approaches are presented for determining linear interaction coefficients for various types of such mineral systems. These approaches are applied to the experimental data and the results are compared. Results accurate within 2 per cent are commonly obtained.

Experimental techniques are discussed and a qualitative and quantitative error analysis is presented. It is shown that the indicated quantities present may not be particularly sensitive to the value of the linear interaction coefficient.

—The dielectric properties of saturated kaolinite clay-water-electrolyte systems were determined over the frequency range of 30–105c/s. Very large dielectric constants are observed at low frequencies. Since the experimental data approach constant values at each end of this frequency spectrum, they can be described by a fairly well defined spectrum of relaxation times. The particle size and orientation, the type and amount of electrolyte, and temperature affect the low frequency dielectric increment and the average relaxtion time. Several physical processes, such as relaxtion due to dipolar rotational polarization, interfacial polarization, free space charge and bound ion polarization, are examined in an attempt to explain the observed data. It is concluded that there exists at present no theory to explain all the data, but the bound ion polarization mechanism appears to explain some of the results.

Sealing with waterborne clays is a rapid and low cost method of controlling seepage through porous media whenever the clay source is within economical shipping distance of the sealing site. But more must be learned about this method of sealing before it can be fully utilized.

Water impedance of waterborne bentonites, as measured by water loss in the filter press test, was correlated with their physical, chemical and mineralogical properties. A multiple linear regression analysis showed clay content and exchangeable sodium percentage (ESP) were most highly correlated with water impedance. Swelling, viscosity and gelation of these clays play only a secondary role in forming a water barrier when used as dilute waterborne sealants as suggested by these and other data.

There were strong positive correlations between water loss and samples high in silt-sized cristobalite, quartz and feldspar; and negative correlations between water loss and samples high in clay-sized montmorillonite, chlorite and illite.

Predicted minimum clay contents (of prospective sealers) were found to be 65–75 per cent clay at 70 and 20 per cent exchangeable sodium, respectively.

Clay mineral studies in the U.S.S.R., mainly since 1960, are summarized. Electron diffraction techniques especially have been developed and used extensively. Methods have been developed for simultaneous recording of DTA curves and other properties. Polytypism of phyllosilicates has been studied intensively by Zvyagin and others. Much new information on the structure and morphology of halloysites has been obtained by electron-optical methods. Other clay minerals extensively studied include allophanes, kaolinites, chlorites (“donbassite” is preferred to “sudoite” for dioctahedral varieties), alushtite (or tosudite), monothermite, and various zinc-bearing clays. Much attention has been given to physico-chemical and colloid-chemical properties. The natural occurrence and alteration of clays and clay minerals are described in weathering and oxidation zones, in soils, and in Recent and Ancient sediments. Primary clay minerals of hydrothermal origin are described.

The effect of orientation of vermiculite particles on the diffusion of Na ion was measured by a tracer technique. The diffusion measurements were made on pellets prepared by pressing freezedried vermiculite in a cylindrical die and the diffusion coefficient evaluated by a thin-film boundary condition of Fick’s law. Because flakes of vermiculite were highly oriented under the pressing force, it was possible to prepare different angles of specimen orientation with respect to the surface where diffusion was initiated. Mathematical relationships of orientation angle, axial ratio of the platelets, and apparent diffusion coefficient were developed. The experimental results on the diffusion of Na ion in K-vermiculite of clay size gave apparent diffusion coefficients of 2·21 × 107cm2 sec−1 when the diffusion flux was parallel with the clay platelets and 0·45 × 10−7 cm2 sec “1 when the flux was perpendicular to the clay platelets. For the diffusion of Na ion into Na-vermiculite, apparent diffusion coefficients were obtained of 1·18 × 10−8cm2sec−1 when the diffusion flux was parallel with the clay platelets, and 0·18 × 10−8 cm2 sec−1 when the flux was perpendicular to the platelets. For K-vermiculite, the change in apparent diffusion coefficient is a simple one of particle geometry. The Na-vermiculite system exhibited more complicated behavior.

Glauconite pellets of vermiform and lobate morphology occur together in Eocene geologic formations in Maryland. Morphologically, the vermiform pellets appear to be identical to those that have previously been called “altered biotite”. In thin sections these pellets do show a well-defined micaceous morphology with the layers running across the worm-like pellets. Some zones in these pellets appear to be “crystals” that are up to 30 × 70 μ and nearly rectangular in cross section. However, there are tiny cracks along cleavage planes within these “crystals”. Externally, the lobate pellets have many rounded lobes and are similar to one of the shapes that Burst has called free-form. In thin section under crossed nicols these pellets have a grainy appearance, indicating that the lobate pellets are composed of many small zones, each about 5–20 μ across. Within these zones the mineral glau-conite has a single orientation, but the zones are not lined up with each other to give the gross micaceous appearance that is associated with the vermiform pellets.

Random powder X-ray diffraction patterns (prepared with a large 114·59mm Norelco powder camera) of individual vermiform and lobate pellets are nearly identical. Eight vermiform and 9 lobate pellets gave the same mean 001 (10·2 Å) and 060 (1·518 Å) spacings. The patterns from both kinds of pellets are similar, except for the absence of some weak lines, to Warshaw’s (ASTM) pattern for glauconite. The patterns have lines indicating a 1 M polytype, however, hkl lines with k ≠ 3n are broad indicating some disorder. In addition to X-ray diffraction patterns, the K2O content (6·7 per cent) and CEC (29 me/100 g as Ca replaced by Mg) of the pellets indicate that interstratified expanded layers may be the main source of the disorder.

If the vermiform pellets are altered mica, the alteration has been sufficient to give a product that is definitely identified as glauconite by X-ray methods. The possibility of mica alteration is suggested by the geographic nearness of the Piedmont (a mica source area) and the occurrence of Piedmont-type quartz with the glauconite pellets. Alternatively, the vermiform pellets may form during glauconite crystallization or recrystallization processes. The probability that both kinds of pellets obtained their morphology before or during, rather than after, the time they became glauconite (mineralogically) suggests that the proper environment may form glauconite from a variety of starting materials.

Plagioclase feldspar is one of the outermost minerals destroyed in the hydrothermal alteration of quartz monzonite of the Butte district, Montana. Single grains of andesine plagioclase showing varying stages of fringe alteration were selected to show the sequence of events leading from the fresh plagioclase tectosilicate to the phyllosilicate montmorillonite, and to evaluate the role of petrographically-identified allophane in the alteration process.

Replicas of fresh, incipiently, and thoroughly montmorillonitized grains reveal a complex sequence of events which may follow alternate equivalent paths. Quantitatively most important is the formation of a hobnail texture composed of sparse to dense ~0.5 μ discoids of amorphous material on feldspar cleavage surfaces. These discoids appear to fuse laterally to form amoeboid or lobate amorphous clusters. Some assume progressively more polygonal outlines characterizing the montmorillonite morphology, or their fringes become flake-like montmorillonite which peels away in wisps from the pitted feldspar surface. Wisps may persist singly, they may form minute ropy granules, they may develop into wispy ridges, or the entire surface may convert to ragged, wispy, or compact montmorillonite. Far less commonly, plagioclase appears to develop without a discernible amorphous stage. The alternative paths are probably influenced by the chemical activity of magnesium in the system.

A deposit of kaolin clay, the site of the General Zaragosa Mine, located about 50 km northwest of San Luis Potosi, S. L. P., Mexico, has produced more than 250,000 tons of refractory clay by room and pillar mining methods during the last 32 years. The clay was formed by hydrothermal argillation of part of a fault block of rhyolite flow-breccia and probably welded tuff, presumably lower Tertiary in age. A silica-rich gossan now exposed at the surface caps the clay deposit.

Samples collected sequentially from the fresh rock to the most highly altered kaolin and studied by optical, X-ray, DTA, and chemical methods, show progressively:

1. Bleaching of the breccia matrix accompanied by mobilization of much of the iron, which was concentrated locally as spots of reddish oxide in the least altered areas.

2. Mobilization, and removal of considerable alkali and alkaline earth metals, in excess of that required to form montmorillonite; mobilization of silica, which was redeposited as fine anhedral quartz crystals disseminated within the montmorillonite and associated kaolinite-halloysite, or developed tripolitic, argillized rock peripheral to the clay ore body.

3. Further desilication of the silica and clay yielding relatively pure, but poorly ordered, kaolinite-halloysite as the most intense end product of argillation. Much silica removed during intense argillation was reprecipitated as tripolitic clay, as minor cristobalite in microscopic globules and massive aggregates characteristic of colloform opal, and in vastly larger amounts as opal and chalcedony replacing the rock overlying the clay (forming a silica gossan).

4. Minor amounts of alunite are present at two places in the deposit, which are interpreted tentatively as being the most probable loci of rising solutions.

The absorption of biologically important purines, pyrimidines, and nucleosides by Li-, Na-, Mg-, and Ca-montmorillonite has been studied in aqueous solutions over a range of pH values 2–12. The initial organic concentrations were about 1 m.molar. The ratio clay to organic compounds was such that only up to 25 per cent of the exchange capacity could be saturated by organic cations, but, depending on conditions, up to 100 per cent of the available organic material was absorbed. Of the nineteen compounds studied, only thymine, uracil, and their nucleosides were not absorbed under the experimental conditions. Absorption occurs primarily as a cation exchange reaction under acid conditions and varies with the basicity of the compounds, their aromatic or non-aromatic character, and the possible extent of their van der Waals interaction with the silicate layers. Nucleosides generally are less strongly absorbed than their purines or pyrimidines because their non-planar structure permits less van der Waals interaction; their absorption is influenced by the differences in swelling behavior of montmorillonite with mono- and divalent cations.