A road log of a 37-mile field trip is presented. The route passed over a group of Early Tazewell moraines and the till plains in between. Stops were made at Flanagan, Drummer and Elliot soil profiles and the type Fithian illite locality. The soil profiles and Fithian cyclothem are described.

Consistency curves and characteristics of Newtonian, pseudoplastic, Bingham body, thixo-tropic and dilatant types of flow are reviewed. The theoretical effects of particle shape on effective hydrodynamic volume and shear resistance for ideal suspensions are considered.

The rheological properties of hydrogen and sodium mono base-exchanged kaolinite clays were determined, using a rotational viscometer, on slips containing up to 50 g solids per 100 g slurry. Changes in rheological properties were also evaluated as a hydrogen slip containing 20 g solids per 100 g slurry was converted into the sodium form.

The discussion includes the effect of differences in charges and charge distribution on the sodium and hydrogen particles and the resulting effects on particle orientation and flocculation. Correction factors for dissociation and particle interference have allowed the use of Einstein’s equation for the viscosity of a suspension up to concentrations of about 40 percent solids for the hydrogen kaolinite system, and about 50 percent solids for the sodium kaolinite system.

A sorption apparatus consisting of (1) a high vacuum system (<10−5 mm Hg), (2) an oil manometer to determine the equilibrium vapor pressure, (3) a quartz helix to determine weight of adsorbate, and (4) a constant temperature control for the adsorption chamber has been used to obtain water vapor sorption isotherms on kaolinite. Equilibrium between water vapor and the clay surface can be obtained in 2 hours with this equipment. The estimated error in relative pressure (P/P0) and amount of water adsorbed (X) are ± 0.001 and ± 0.07 mg H2O/g clay respectively. Reproducibility of sorption isotherms for clay samples similarly prepared are within these limits. When retested those clay samples that had stood in the laboratory for a few weeks gave sorption isotherms slightly different from the initial isotherm. This variation, while not excessive, seriously limited interpretation of the sorption data.

In order to study the variation of sorption characteristics with curing conditions, two samples were stored at an elevated temperature (70°C) under two different conditions of moisture content and pressure; one sample as a water slurry (1 g clay per 10 ml H2O) and the other completely dry in an evacuated (<10−5 mm Hg) container. The effect on the sorption isotherms was in both cases very marked but of a different character.

Compared with the sorption behavior of the initial Li kaolinite, the sample stored as a slurry showed greater water adsorption at all values of P/P0 and a disappearance of the marked hysteresis which persists to very low P/P0 on the initial sample; however, when stored in vacuo, Li kaolinite at all values of P/P0 adsorbed less water than the initial Li kaolinite. Data are presented to show that the sample stored as a slurry has been converted to an Al kaolinite. The reduced water sorption upon storage in vacuo is shown to be a permanent change.

In the intermountain states, a region deficient in kaolinite and alumina clays, there is an increasing demand for refractory clay. In this arid region residual kaolins are not developed in quantity from feldspathic intrusives. Glassy, siliceous extrusives alter commonly to mont-morillonite of the montmorillonite-beidellite series. Zeolites, principally analcime and heu-landite, often are alteration products. Under certain conditions kaolinite, halloysite, or saponite will form; several tuffaceous deposits were investigated in an attempt to determine these environmental conditions, especially the physico-chemical environment necessary to produce kaolin clay.

Zeolites are developed where the pyroclastics are deposited in an alkaline lake; saponite is formed locally in this environment as a result of hot-spring activity. On river slopes and spurs the siliceous volcanics alter to kaolinite and montmorillonite; where associated with calcareous hot-spring activity in a fresh-water lake, halloysite results. Montmorillonite-beidellite develops where these special conditions do not obtain.

The prospects of finding a residual kaolinite deposit developed from siliceous volcanics are not good. Hydrothermal alteration appears to be the only means by which a siliceous volcanic will be converted to a sizeable refractory clay deposit in this region.

In the oil industry it has been customary to describe water loss or filtration from benton-ite drilling fluids by adaptation of Darcy’s law to the filtration process. Thus, the rate of filtration varies directly with the differential pressure and permeability and inversely with the filtrate viscosity and the thickness of the deposited filter cake. Since the thickness of the filter cake is variable, however, it is necessary that the rate of deposition of the filter cake be related to the volume of filtrate. In establishing this relation certain workers have made questionable allowance for the water adsorbed on the bentonite particles with the result that the filtration equation is not valid in certain instances (Larsen, 1938; Rogers, 1953, p. 268).

Other workers have indicated the significance of the adsorbed phase in their presentation of experimental techniques for relating the filter cake and the filtrate (Williams and Cannon, 1938; von Englehardt, 1954).

The filtration relationship may be derived analytically by the simultaneous use of Darcy’s law and mass and volumetric balances on the filtration process. Such a derivation is here presented. The validity of the filtration relationship presented is experimentally confirmed using three groups of unlike systems—Wyoming bentonite suspensions, low-yield clay suspensions, and sodium carboxymethylcellulose suspensions—as well as four sets of clay filtration data from the literature.

The concept of surface conductance and its role in the interpretation of the formation resistivity factor of reservoir rocks is reviewed.

The specific surface conductance of a clay is determined for four narrow particle-size fractions of sodium Wyoming bentonite in conductivity water. The values are derived from the specific conductance of gels of these clays on the basis of the picture of an idealized cubic network structure of the clay plates. The average surface conductance for internal and external surfaces of the bentonites is found to be 3.2 × 10−19 ohm−1, which is 0.55 × the value expected when all exchangeable ions are assigned their infinite dilution mobility. The data are independent of particle size.

In addition, conductivity data are presented for clay suspensions in a wide range of concentrations. In extremely dilute suspensions, the contribution of the clay to the conductivity when expressed per unit weight of clay (the so-called “weight conductance”) is smaller than expected from an independent movement of particle and counter ions. This is interpreted to be partly a result of both electrophoretic and relaxation retardation, indicating that the electrical double layer on sodium bentonite has a condensed character. Probably part of the counter ions are entirely immobilized by adsorption on the surface.

With increasing clay concentration, further compression of the double layer increases the retardation effects and a further decrease of the weight conductance is observed. A minimum is reached at a concentration of a few tenths of one percent clay at which, according to viscosity and light absorption data, particle interaction becomes apparent. At this point, immobilization of the particles and bridging between the electrodes gradually eliminate the retardation effects, and surface conductance takes over. The weight conductance increases gradually until a constant value is reached in a concentration range of 5 to 12 g of clay per 100 ml gel, from which the above value of the specific surface conductance was computed.

Analyses of samples of kaolinitic, illitic, and montmorillonitic clay materials exposed to artificial sea water for periods of six months to five years have yielded some evidence to support the contention that chloritic and illitic clay types may ultimately develop from montmorillonitic material in the marine environment. However, no indications of the initiation or induction of any major lattice alteration of the original kaolinite and illitic type structures have been recognized on the basis of the data collected.

The techniques of electron diffraction, electron microscopy, x-ray diffraction, and chemical analysis were employed to detect and measure the extent of modification of the clay materials at selected time intervals during the five year period.

Actual separations of illitic-like and chloritic-like materials from treated montmorillonitic material were accomplished by gravitational settling methods. Relative weight percents of 18.2 for chloritic clay separates and 4.4 for illitic clay separates were obtained after more than four years of treatment. Chemical analysis and electron microscopy data suggest that lattice alteration preceded the development of forty to seventy percent of the chloritic and illitic material separated.

The chloritic material apparently developed by initial formation of a magnesium-enriched montmorillonite having a hectoritic appearance. Subsequent development of threadlike extensions from the magnesium montmorillonite is shown by electron micrographs. These threads were observed to decrease or equilibrate in apparent amount within the chloritic separates as platelike forms began to appear after three years. The illitic separates were characterized by fine granulai material with increasing occurrence of larger platelike forms as exposure time increased.

The modification of montmorillonitic clay was observed to be more dependent upon the magnesium-potassium ratio in the sea water than upon the total salt concentration levels. The limiting magnesium-potassium ratio was found to be approximately 9.4 with a limiting low potassium concentration of 0.005 moles per liter for montmorillonitic material of less than 0.5 micron settling diameter. The alteration of the montmorillonitic material was noted only for material that was initially settled through the artificial sea water media. As the potassium concentration level of these media dropped by extraction below 0.005 molar, a bulk effect of the settling material became operative and the relative percent of altered material decreased.

Further, the relative amounts of modified material detected were decreased by the introduction of carbohydrate material into the sea water media. The amounts present after a definite time interval were also observed to be dependent upon the distributive tendencies of the source materials and the physical disturbance of the sea water media. Resuspension of the material by reagitation of the system decreased and significantly governed the rate of diagenetic modification.

Special electron micrographs are presented to illustrate relative stages of flocculation of montmorillonitic material as the ionic concentration of sea water increases. It is suggested that these stages govern to an appreciable extent the extent and rate of initiation of any ionic exchange and lattice changes that occur.

Glauconitic mica occurs as interstitial clay in a bed of fine-grained sandstone, 15 feet thick, in the upper part of the Brushy Basin shale member of the Morrison formation of Late Jurassic age on Blue and Lone Tree Mesas near Uravan, Montrose County, Colorado. This glauconitic mica, similar to other material ordinarily called glauconite, is interesting because the Morrison formation is generally regarded as nonmarine in origin, whereas glauconite commonly forms in a marine environment.

The identifying properties of the glauconitic mica are: strong 001 d spacing, 9.97A; very weak 002, 5.01A; strong 003, 3.34A; 060, 1.51A; green color, pleochroic; X and Z indices, approximately 1.578 and 1.600; SiO2 49 percent, Al2O3 18 percent, Fe2O3 13 percent, FeO 1.3 percent, MgO 2.8 percent, K2O 7.8 percent, TiO2 1.1 percent, ignition loss 6 percent, others approximately 1 percent.

The glauconitic sandstone is underlain by variegated mudstones about 480 feet thick, which contain montmorillonite (with very sparse relicts of shards), illite, quartz, and also, in several layers, scanty analcime. The Burro Canyon formation of Early Cretaceous age overlies the glauconitic sandstone.

This paper discusses alternative origins of the glauconitic mica possible within the framework of an appropriate chemical environment other than, and apart from, one typically marine.

The tubular structure that has been proposed for endellite [Al2(OH)4Si2O5·2H2O] will contain considerable space not occupied by the solid phase. Based on the tubular dimensions which have been reported for this material, void space of 30 to 40 percent of the total volume of massive endellite would be anticipated.

Experimental determination of the void space in several samples of an endellite specimen by means of density measurements made on water-saturated samples indicates that the massive mineral contains 10 percent or less void space. It is concluded that endellite does not exist in a tubular form.

When endellite dehydrates to form halloysite [Al2(OH)4Si2O5] there is no appreciable change in the gross volume of the material. The massive halloysite formed however, contains more than 40 percent void space which is refillable with water. It is hypothesized that endellite may exist in the form of laths with some displacement of the fundamental layer structure. When the endellite dehydrates the laths undergo considerable shrinkage and distortion to give the structures observed in electron micrographs and shadow-cast replicas.

Hydrothermal studies have failed to yield synthetic attapulgite or sepiolites in the system MgO-Al2O3-SiO2-H2O. However, the natural minerals can be decomposed to yield mont-morillonoids by mild hydrothermal treatment as low as 200°C and probably as low as 100°C. These data indicate that they are metastable and probably could not have formed at these temperatures.

Dry dehydration at 400° and 750°C gave no evidence for the presence of “zeolitic water” in these minerals and failed to establish the existence of “anhydride” phases. The field study of relationships in one sepiolite locality suggests the importance of structural control in the formation of these minerals.

The formation of siliceous phases in montmorillonites at temperatures up to 1500°C has been studied by high temperature continuous x-ray diffraction techniques. Oriented clay aggregates on platinum slides are heated in a small platinum-wire resistor furnace placed on an x-ray spectrometer unit. The intensity of the main diffraction lines of each phase is noted versus the temperature. The nature and the temperature of formation of the different phases are closely related to the structure and composition of the sample. The important role of some cations in exchange position is emphasized.

X-ray analyses of the clay minerals from thousands of sediments indicate that any of the major clay minerals can occur in abundance in any of the major depositional environments and there is no consistent coincidence between specific clay minerals and specific depositional environments. It is concluded that the great majority of clay minerals in sedimentary rocks are detrital in origin, strongly reflect the character of their source material, and are only slightly modified in their depositional environments.

The most common process acting on the clay minerals in marine environments is cation adsorption. The modifications produced by this process are secondary but because of the overemphasis of names rather than processes, they have been considered fundamental changes and the process has been called diagenesis. From the geologist’s viewpoint, the basic clay mineral lattice, which is inherited from the source material, is the most significant parameter of the clay minerals and modifications caused by the adsorbed cations are secondary, derived parameters reflecting the character of the depositional environment. This concept of dualism is essential to the understanding of clay genesis, and the significance of the two parameters must be understood before a genetic classification can be constructed and before clays can be used for geologic interpretation.

Replacement of alumina by ferric iron in the lattice structure features the nontronite member of the montmorillonite group. Chromium, in significant amounts, replaces ferric iron in the lattice structure of some nontronites.

Effect of migration of clay minerals under colloidal suspension and the transfer of true solutions complicate correlations of the chemical composition. Moreover, many nontronites are secondary and occur in fracture zones associated with kaolinitic and halloysitic clay. A tendency of certain nontronites to form lathlike crystals is well known.

Chemical composition of 15 selected nontronites from the United States of America, Germany, and Russia indicate a range of 30 to 60 percent SiO2, and a range of from 25 to 40 percent Fe2O3. Minor constituents are the oxides of magnesium, titanium, ferrous iron, and calcium, and the alkalis, potassium and sodium.

Magnesium percentages found in nontronites are proportional to the value of sigma for octahedral coordination. Ferrous iron is proportional to titanium in montmorillonite, and a similar relationship is observed in the nontronites.

A deficiency in alkalis typifies the composition of montmorillonite and this condition is likewise true in most nontronites. Potassium is limited to a narrow statistical range of between 0.5 to 0.6 ions of Al in tetrahedral coordination against an extreme deficiency of ferric iron and magnesium (combined) of less than 0.05 ion in octahedral coordination. Thus calcium occurs as the principal large cation and is present in nearly all the nontronites studied.

Synthetic resins offer a possible method of soil stabilization for roads; aniline-furfural is a synthetic resin showing commercial possibilities. Differential thermal analysis is a useful tool for interpreting the relation between aniline-furfural and the soils that have been stabilized by this resin.

Differential thermal curves were run on several loess soils that had been stabilized with varying amounts of aniline-furfural. The clay fraction of these soils had previously been identified as predominantly interlayered illite-montmorillonite minerals. The <2 micron clay fraction varied from 7.4 to 37.0 percent. The thermal curves showed characteristic exothermic organic reactions in the treated soils and relationships were found between the thermal reactions, the percent aniline-furfural, and the percent clay.

Double peaks were observed on the curves of all soils containing 2 percent or more of aniline-furfural. The area under the organic double peaks was found to be a function of the percent aniline-furfural. The double peak is believed to be caused by initial burning of readily available aniline-furfural followed by final burning of the remaining aniline-furfural. The release of the resin responsible for the second peak may be due to a breakdown of the clay crystal structure at about 550° C. This indicates a close association of the resin and the clay minerals. The foregoing statement is further strengthened by a linear correlation of distance between peaks and the amount of clay present. Higher aniline-furfural contents increase the area under the second peak; this increase indicates that a larger amount of the resin is being utilized in cementation of grains and is reflected by the mechanical strength of stabilized soil specimens.

Studies on clay types in the soils of Arkansas show differences that are important to the soil properties in the soils of the various regions. Part of the agricultural importance of these soils may be related to their mineralogical composition.

The Mississippi River delta area has deposits of soil materials high in montmorillonite-type clay and possessing strong expansion and shrinkage properties. The Arkansas River valley has materials high in illite clay types with montmorillonite. Soils of the Coastal Plain predominate in kaolinite mineral but have sufficient quantities of vermiculite clay to dominate the chemical properties. The Ozark upland soils contain kaolinite and illite in varying proportions.

Much of the state is covered with a silt mantle of varying thickness in which the clay mineral composition is mainly that of montmorillonite and illite.

A study was made of the weathering of musco vite-type mica to dioctahedral vermiculite in soils formed from Wissahickon schist in the Piedmont of Virginia. The trend of weathering as a function of depth was most apparent in the soil fractions from 20 to 0.2 microns. X-ray diffraction and chemical analyses indicate loss of potassium and expansion of the muscovite to form vermiculite as weathering proceeded. The amount of interstratified illite-vermiculite relative to vermiculite varied greatly between three soils and was characteristic for each. The widespread occurrence of dioctahedral vermiculite in highly weathered and acid soils suggests the formation of this mineral from commonly occurring muscovite-type micas.

Mineralogical analyses were made of the day, silt, and sand fractions of the Podzols Hiawatha loamy sand and Hiawatha sand. The layer silicates show chemical weathering as a function of depth in both soils. A high charge dioctahedral montmorillonite was dominant in all fractions (−5µ) of the A2 horizon and its origin was attributed to weathering of an interstratified vermiculite-chlorite similar to that in the B2 horizon. The 2 to 0.2µ fraction of the Hiawatha loamy sand B2 horizon contains 14 percent chlorite and 18 percent vermiculite with no montmorillonite, and the Hiawatha loamy sand A2 horizon contains 33 percent montmorillonite with little interstratified chlorite-vermiculite. Quartz also showed a soil depth function in the fine silt. It is higher in amount in the A2 than the B2 horizon, attributable to its relative stability in the Podzol A2. Below the B2 it drops markedly in amount, attributable to a difference in silt deposition.

The similarity of ratios of resistant heavy minerals (greater than 2.95 sp. gr.) in different horizons indicates uniform origin of the sand fractions of these soils. Light mineral contents in the sand fractions for all analyzed horizons are also similar. However, particle size data indicate silt and possible clay addition to both the A2 and B2 horizons.

Depth functions in these soils are developed to a marked extent, apparently owing to (1) low amount of fine fraction originally present for weathering, (2) greater amount of water cycled through the A2 than the B2 horizon, (3) rapid and frequent cycling of available water owing to coarse texture, and possibly (4) effects of podzolization. The Omega, Ahmeek, and Iron River soils of northern Wisconsin also showed a similar though not so marked tendency to accumulate montmorillonite in the A2 horizon.

Controversy over the origin of clay minerals in ancient sediments arises because it is difficult to segregate the factors that cause differences in clay mineral composition. A plan of sampling based on four contrasts was used to evaluate some of these factors. Contrasts studied were: (1) permeability contrasts (sandstone vs. shales); (2) environmental contrasts (cyclic sedimentation); (3) weathering contrasts (outcrop vs. core); (4) source area contrasts (orthoquartzite facies vs. subgraywacke facies).

The resultant data indicate that clay minerals are both allogenic and authigenic. Allogenic clay minerals are the rule when inheritance from the source area dominates either postdepositional or environmental effect; authigenic clay minerals are found where the environment dominates. Rapid sedimentation favors a dominance of allogenic clay minerals, and major depositional environmental effects are required to produce appreciable change. Some of the factors that influence clay mineral composition include source area contribution, the depositional environment, postdepositional effects after burial, permeability, and postdepositional weathering effects.

At the Desmoinesian-Missourian disconformity in southeastern Kansas a fossil soil zone is recognized by variations in clay mineralogy in the uppermost Desmoinesian Holdenville shale, which underlies basal Missourian Hepler sandstone. The clay fraction of the overlying basal Missourian Hepler sandstone contains kaolinite, slightly hydrated illite, quartz, and vermiculite. Chlorite (rather than vermiculite) is present in shaly portions of the basal Hepler sandstone. Clay-size minerals of the typical Holdenville shale (marine) are predominantly illite, chlorite, quartz, feldspar, and a very small quantity of kaolinite. The clay-mineral assemblages in samples from the upper part of the Holdenville shale indicate hydration of illite, sporadic increase in kaolinite, possible decrease in feldspar, and progressive modification and destruction of chlorite resulting in production of mixed-layer minerals.