Dioctahedral Chlorite Research Articles

Mineralogy, Mineral Chemistry and SWIR Spectral Reflectance of Chlorite and White Mica

Hyperspectral reflectance has the potential to provide rapid and low-cost mineralogical and chemical information that can be used to vector in mineral systems. However, the spectral signature of white mica and chlorite, despite numerous studies, is not fully understood. In this study, we review the mineralogy and chemistry of different white mica and chlorite types and investigate what mineralogical and chemical changes are responsible for the apparent shifts in the shortwave infrared (SWIR) spectroscopic absorption features. We demonstrate that the spectral signature of white mica is more complex than previously documented and is influenced by the Tschermak substitution, as well as the sum of interlayer cations. We show that an increase in the interlayer deficiencies towards illite is associated with a change from steep to shallow slopes between the wavelength position of the 2200 nm feature (2200 W) and Mg, Al(VI) and Si. These changes in slope imply that white micas with different elemental chemistry may be associated with the same 2200 W values and vice versa, contrary to traditional interpretation. We recommend that traditional interpretations should only be used in true white mica with sum interlayer cations (I) > 0.95. The spectral signature of trioctahedral chlorite (clinochlore, sheridanite, chamosite and ripidolite) record similar spectral relationships to those observed in previous studies. However, dioctahedral Al-rich chlorite (sudoite, cookeite and donbassite) has a different spectral response with Mg increasing with 2250 W, which is the opposite of traditional trioctahedral chlorite spectral interpretation. In addition, it was shown that dioctahedral chlorite has a 2200 W absorption feature that may introduce erroneous spectral interpretations of white mica and chlorite mixtures. Therefore, care should be used when interpreting the spectral signature of chlorite. We recommend that spectral studies should be complemented with electron microprobe analyses on a subset of at least 30 samples to identify the type of muscovite and chlorite. This will allow the sum I of white mica to be obtained, as well as estimate the slope of 2200 W absorption trends with Mg, Al(vi), and Si. Preliminary probe data will allow more accurate spectral interpretations and allow the user to understand the limitations in their hyperspectral datasets.

Origin of dioctahedral smectites in Lower Eocene Lulehe Formation paleosols (Qaidam Basin, China)

Smectites affecting water and soil exchangeable cations, especially potassium and ammonium related to plants, are common swelling clay minerals in sediments and paleosols that can record paleoenvironmental and paleoclimatic information. Paleoenvironmental and paleoclimatic interpretations are potentially ambiguous, because smectite minerals may have either detrital or pedogenic origins. This study analyzes smectites in Lower Eocene paleosols of the Qaidam Basin, China, with the goal of determining their origin and paleoclimatic significance. Twelve smectite-rich vertisol samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) in the Dahonggou (DHG) section of the Lulehe Formation. The samples from DHG section contained predominant dioctahedral smectites (60–65%) in the <2 μm clay fractions. Minor dioctahedral illites, dioctahedral interstratified illite-smectite (I-Sm), kaolinite, and traces of dioctahedral chlorites and palygorskites were present. The chemical data and FTIR spectra revealed both tetrahedral substitutions (i.e., Al for Si) and octahedral substitutions (i.e., Mg and minor Fe for Al) in the dioctahedral smectites. Montmorillonite comprised the dominance of the fine-clay fractions (< 0.2 μm) with minor contributions of beidellite, as determined by the Greene-Kelly test (GK-test), geochemical and FTIR analyses. SEM observations revealed two morphological types of dioctahedral smectites, the less abundant one with typical ‘honeycomb’ structure, interpreted as neoformed, and the other occurring as thin, well-defined plates and irregular masses considered to be detrital. DSC revealed two dehydroxylation temperatures (500–550 °C and 600–700 °C), indicating the presence of trans-vacant (tv) and cis-vacant (cv) layers, respectively. The cv layers were attributed to montmorillonite originating as catchment-delivered detritus, as the study Lulehe Formation exhibited no evidence of volcanic ash layers or diagenesis that would have promoted formation of montmorillonite with high dehydroxylation temperatures. The tv layers represented pedogenic beidellite formed via solution crystallization in a floodplain pedogenic environment. The accumulation of abundant inherited montmorillonite and neoformed beidellite in paleosols of the Lulehe Formation was probably promoted by a relatively warm climate with alternating wet-dry seasons during the Early Eocene. Admixture of detrital montmorillonite makes paleoclimatic reconstructions based on bulk-smectites concentrations and isotopic compositions unreliable, showing that integrated clay mineralogical analyses of the type undertaken in this study are necessary to identify the provenance and paleoclimatic significance of smectites in sediments.

Mineralogical and geochemical features of pyrite nodules of sulfide turbidites from the Talgan Cu–Zn massive sulfide deposit (South Urals)

Pyrite nodules were found in thin-layered sulfide ores localized at the flanks of the Talgan Cu‒Zn massive sulfide deposit (South Urals). The nodules consist of (1) an inner core of microgranular pyrite with inclusions of authigenic sulfides and host rock minerals, (2) an intermediate zone of anhedral and subhedral pyrite metacrystals, (3) an outer zone formed by parallel subhedral pyrite crystals and (4) dioctahedral chlorite rimming the pyrite crystals of zone 3. Each zone exhibits specific trace element association, which is identified using LA ICP-MS micromapping. The trace element content of pyrite significantly (by 13 orders of magnitude) decreases in a range of microgranular pyrite of the core an- and subhedral pyrite crystals of the intermediate zone subhedral pyrite crystals of the outer zone (average values, ppm): 131069 Zn, 241001783 Pb, 1323134 As, 10271.81 Co, 4564 Ni, 39038 Ag, 0.10.01 Au, 550.6 Te, 9.80.6 Bi. The subhedral pyrite crystals of the outer zone are enriched (ppm, up to) in Cu (8367), Sb (1627) and Mn (734) relative to microgranular pyrite of the core. The extremely high trace element contents are related to the inclusions of authigenic chalcopyrite, sphalerite, fahlore, gold and silver minerals. The host rock components of the nodules include quartz, calcite, chlorite, illite and REE minerals. The ore clasts of distal sulfide turbidites mixed with hyaloclastites, which were altered during dia- and anadiagenesis, were the source of ore material for the nodules.

Thermal decomposition of Ferrian chamosite: an infrared emission spectroscopic study

The thermal behaviour of ripidolite, an iron-rich chlorite, has been studied in situ by infrared emission spectroscopy up to 800 °C. The more di,trioctahedral nature due to significant amounts of Fe3+ is reflected, in addition to the two bands around 3420 and 3560 cm−1, by an extra band around 3345 cm−1. This extra band is absent in pure dioctahedral chlorites without Fe3+. These bands have been assigned to (AlAl)O-OH, (SiAl)O-OH and (SiSi)O-OH stretching modes with increasing frequencies. The bands disappear upon dehydroxylation around 650 °C. A similar behaviour is observed for the corresponding libration modes around 716, 759 and 802 cm−1. The stretching and bending modes of the inner-OH of the octahedral sheet in the 2:1 clay-like layer are observed around 3645, 943 and 904 cm−1. Although the bands decrease in intensity, they remain present up to 800 °C as dehydroxylation of the octahedral sheet is not yet complete at this temperature. The presence of two bending modes is explained as being due to a differentiation between Mg-OH and Fe-OH modes. At 650 °C a new sharp band is observed around 502 cm−1 assigned to a (Fe,Mg)-O-Al bending mode caused by the formation of a spinel-like interlayer phase after dehydroxylation.

Seafloor hydrothermal clay alteration at Jade in the back-arc Okinawa Trough: mineralogy, geochemistry and isotope characteristics

Seafloor hydrothermal activity at Jade has resulted in extensive alteration of the host epiclastic sediments and pumiceous tuffs, forming mica, kaolins (kaolinite and halloysite), Mg-rich chlorite, talc, montmorillonite, and a mixed-layer mineral of dioctahedral chlorite and montmorillonite (Chl/Mont). Clay mineral assemblages show a vertical variation, which reflects variable amounts of cold seawater incorporated into hot hydrothermal fluids in subsurface sediments and tuff. However, mixing alone cannot explain the occurrence of abundant kaolin minerals at Jade. The formation of kaolin minerals requires much more acidic fluid than expected from simple mixing of hydrothermal fluids and cold seawater. Low pH values are likely attained by oxidation of H 2S either dissolved in the hydrothermal fluid or released from the fluid during decompression. The fluid reaching the seafloor is discharged into cold seawater, which caused precipitation of sulfides close to vents and native sulfur and barite at the margins of the vent areas. Halloysite, barite and anhydrite show Sr isotope compositions similar to marine Sr, indicating the derivation of marine Sr directly from seawater or by the dissolution of calcareous nannoplanktons. The isotopic compositions of kaolinite (δ 18O = +7.4‰, δD = −23‰), Chl/Mont (δ 18O = +7.0‰, δD = −32‰), and mica (δ 18O = +5.4 to +9.9‰, δD = −30 to −26‰) suggest fluids of a heated seawater origin. The O isotopic data yielded formation temperatures of 170°C for kaolinite, 61 to 110°C for halloysite, and 145 to 238°C for mica. Barite δ 34S values (+21.0 to +22.5‰) are very similar to the marine sulfate value, confirming that the barite formation took place due to mixing of Ba-bearing hydrothermal fluids and sulfate-rich seawater. Native sulfur shows a large variation in δ 34S in one hand specimen probably because of rapid disequilibrium precipitation of S during fluid exhalation on the seafloor. Sulfur in hydrothermal fluids is usually consumed to form metal sulfides. Therefore, abundant native sulfur at Jade suggests high H 2S/metals ratios of the hydrothermal fluids. The alteration assemblages and isotopic data of hydrothermal minerals from Jade are very similar to those of Kuroko-type barite deposits of middle Miocene age, which formed from fluids of high S/metals ratios at less than 200°C. At Jade, there is only one black smoker actively discharging high temperature (∼320°C) fluid, but there are many fossil sulfide chimneys and mounds in the area. The mineralogy and high Au and Cu in these precipitates suggest highly metalliferous hydrothermal activity in the past. These activities likely resulted in discharge of hydrothermal plumes and fall-outs of sulfides and sulfates on the seafloor. These fall-outs were incorporated in sediments far from the vent areas. They are now recorded as high metal contents in sediments with no petrographic and mineralogical evidence of in-situ hydrothermal activity. Some are high as 8,100 ppm for Cu, 12,500 ppm for Zn, 1,000 ppm for As, 100 ppm for Ag and 21,000 ppm for Pb. Detrital grains of montmorillonite in such sediments are coated with Fe-oxyhydroxides during the suspension in seawater before settling on the seafloor. The depths of such metal anomalies in sediments suggest high levels of metalliferous hydrothermal activities from 1,800 to 300 ybp.

Cloritas dioctaédricas asociadas a piritas en metapelitas de la Sierra de los Cameros

A mineralogical and dynamic-vibrational characterization of a dioctahedral chlorite associated with the Navajun pyrite in the Wealdian of Sierra de Los Cameros (La Rioja), was carried out. The chemical analysis by A.A. and XRF combined with those of punctual character (EDX) allow us to establish the following mean structural formula: (Si 3,32 Al 0,68 ) (Al 3,78 Fe 3+ 0,04 Mg, 0,03 Ca 0,02 K 0,03 Na 0,03 Li 1,04 ) O 10 (OH) 8 from XRD analysis the la-2 polytype was deduced as the most probable one. The most remarkable characteristics of the IR and Raman spectra, compared with those of the dioctahedral chlorites, correspond to the shift of the absorption band in rhe 1.000 cm -1 region and its greater complexity, both related with the Al content.

Clay mineralogy of soils formed in tuffaceous greywacke, Southland, New Zealand, in relation to genesis, soil properties and classification

The clay mineralogy of 12 soils (Dystrochrepts, a Eutrochrept, a Cryochrept and a Placaquept) formed in tuffaceous greywacke parent rocks is presented and discussed. In a New Zealand context, the soils are unusual because of their base-rich parent material which has been partly pre-weathered to smectite and kaolin minerals in geological time. Superimposed on this assemblage are the affects of present climate and soil drainage, which have altered smectite and vermiculite to dioctahedral (aluminous) chlorite. Conventional laboratory treatments cause dioctahedral chlorite to revert fully to smectite or vermiculite, or alternatively partially to interlayered hydrous mica. The labile nature of the interlayer Al is evident in high KCI-Al values. Allophane and gibbsite occur in acid upland soils that are also trace-element deficient. More intense leaching of upland soils with respect to lowland soils accounts for the upland soils' clay mineralogy and trace element deficiencies. The soils fall into three mineralogy classes of Soil Taxonomy and six classes of the proposed Whitton and Childs revision. The classes are not readily usable in the field, and subgroup or family distinctions based on simple chemical tests are suggested.

A study of two soil development sequences located in a montane area of Canterbury, New Zealand, I. Clay mineralogy and cation exchange properties

Field and laboratory data for eight soils, comprising two soil development sequences in a montane area of Canterbury, are presented. The soils are a sequence of five soils developed in fluvial deposits overlain with loess on a streamcut terrace flight (the T soil sequence), and a sequence of three soils developed in moraine deposits of different ages overlain by loess (the M soil sequence). Soils in the T soil sequence represented those forming in the drier zones, and soils in the M soil sequence represent those forming in the wetter zones of this montane area. As the sites were selected so that soil parent materials were derived from the sedimentary rocks of the Canterbury Suite, differences in soil development between the sequences reflected the influence of climate and vegetation factors. Laboratory data obtained include: clay mineralogy, determined by X-ray diffraction and selective dissolution analysis; and pH, cation exchange capacity (CEC), and effective cation exchange capacity (i.e. CEC at soil pH). These data show trends related to climate, vegetation history and soil age, and are discussed in terms of the development of soil acidity and the dissolution and subsequent reactions of Al and Fe. Three clay mineral suites were identified: the first was represented by mica, trioctahedral chlorite, randomly interstratified phases and dioctahedral chlorite, with minor amounts of vermiculite, allophane and gibbsite; the second suite was similar to the first, but contained significantly higher amounts of gibbsite; and the third was represented by mica, vermiculite and smectite in the topsoils, and mica, dioctahedral chlorite, randomly interstratified phases, gibbsite and allophane in the B horizons. Cation exchange properties were characterized by increasing saturation of the exchange complex by aluminium cations, and increasing concentration of base cations in the topsoil.

Crystallochemical classifications of phyllosilicates based on the unified system of projection of chemical composition: II. The chlorite group

AbstractThe classification and nomenclature of chlorites have been critically reviewed. A new classification based on the unified projection system of chemical composition has been proposed in which for the first time all trioctahedral, di-trioctahedral and dioctahedral species are included. The chemical composition of chlorites is controlled by the general crystallo-chemical formula: This is superior to the known formulae for the trioctahedral and dioctahedral chlorites. It has been shown that the chlorite end-member compositions of Bayliss (1975) project in one point of the projection field leaving many end-member compositions unnamed. As they correspond to the names used previously, a proposal is made to restore these names.

Structures, Compositions, and X-Ray Diffraction Identification of Dioctahedral Chlorites

AbstractAl-rich di, trioctahedral chlorite exists as the species cookeite and sudoite. Di,dioctahedral chlorite exists as the species donbassite. Cookeite has essential Li in its structure, sudoite has essential Mg, and donbassite has only small amounts of either element. To date, sudoite has been reported to have only IIb structural units and donbassite to have only Ia structural units. Cookeite is based primarily on Ia structural units, but IIb units are present in specimens from two localities. Most Al-rich chlorite species have regular-stacking “r” or “s” 2-layer stacking sequences, but 1-layer Ia-2 and Ia-6 polytypes also are known. The structural units (Ia or IIb) and the specific stacking sequences can be explained by a combination of local charge balance and minimization of cation-cation repulsion involving the interlayer and tetrahedral cations. X-ray powder diffraction data are adequate to differentiate Al-rich chlorite from trioctahedral chlorite and to identify the type of structural unit present, but single crystal study is necessary to identify the 2-layer and 1-layer sequences with certainty.

Lithium-Bearing Donbassite and Tosudite from Echassières, Massif Central, France

AbstractLithium-bearing donbassite and tosudite were found in veins in hydrothermally altered granite (Beauvoir granite) in the northern part of the Massif Central, France. The two minerals are characterized by their high Li contents and low Mg and Fe contents; their structural formulae are: $${\left( {S{i_{3.81}}A{l_{0.19}}} \right)_{\Sigma = 4.00}}{O_{10}}{\left( {A{l_{3.81}}L{i_{0.52}}Fe_{0.01}^{2 + }C{a_{0.02}}M{g_{0.01}}} \right)_{\Sigma - 4.38}}{\left( {OH} \right)_8}{\left( {N{a_{0.07}}{K_{0.04}}} \right)_{\Sigma = 0.11}}$$ for donbassite and $${\left( {S{i_{3.50}}A{l_{0.50}}} \right)_{\Sigma = 4.00}}{O_{10}}{\left( {A{l_{2.95}}L{i_{0.22}}Fe_{0.01}^{3 + }T{i_{0.01}}} \right)_{\Sigma = 3.19}}{\left( {OH} \right)_5}{\left( {C{a_{0.01}}N{a_{0.15}}{K_{0.18}}} \right)_{\Sigma = 0.34}}$$ for tosudite.These chemical compositions indicate that the donbassite is an intermediate member of the donbassite-cookeite solid solution series and that the tosudite consists of interstratified Li-donbassite and beidellite. Both Li-bearing minerals show thermal behavior distinct from those previously reported for dioctahedral chlorite and tosudite.Petrographie investigation of drill cuttings from the Echassières area indicates that the two minerals were formed in an intermediate stage of hydrothermal alteration following an early stage characterized by formation of muscovite (2M1) at &gt;350°C and before the latest stage characterized by deposition of kaolinite and randomly interstratified illite/smectite at &lt; 100°C. Moreover, tosudite occurs in the upper part of the granite, whereas donbassite is restricted to the lower part, suggesting the formation of tosudite at lower temperatures.

Structural Data for Sudoite

AbstractSingle crystals of sudoite from Ottré, Belgium, allow confirmation of a dioctahedral 2:1 layer and a trioctahedral interlayer in a IIb arrangement. A regular 2-layer s structure is formed in which the octahedral stagger within both 2:1 layers is directed along X1 and adjacent layers are alternately displaced by a2/3 and a3/3. Poor quality crystals and twinning prevented three-dimensional refinement. One-dimensional refinement suggests that the smaller d(001) value of dioctahedral chlorites relative to trioctahedral species is due primarily to the thinner dioctahedral sheet.

Hydrothermal clay mineral formation in a biotite-granite in northern Switzerland

AbstractClay minerals of several hydrothermally altered zones in a 1200-m biotite-granite core from a drillhole in northern Switzerland were studied microscopically, by XRD and by electron microprobe. The minerals principally affected by the hydrothermal alteration were plagioclase (An5-An20) and, to a lesser extent, biotite. Illite, regularly interstratified illite-smectite and dioctahedral chlorite-smectite, dioctahedral chlorite, trioctahedral chlorite and kaolinite were detected in the alteration products. Commonly, two or more clay minerals occurred together in pseudomorphs after plagioclase. The mineral chemistry of the clay minerals showed a predominance of the substitution KAl for Si and, to a lesser extent, MgSi for Al. Fluid-inclusion data and the absence of pure smectite and epidote indicated temperatures of ∼200°C for the fluid that caused this alteration.

Dissolved Al in sediments and waters of the East China Sea: Implications for authigenic mineral formation

Numerous previous studies indicate that several different authigenic aluminosilicates form in the oceans. In this study we show, using dissolved Al distributions in sediments and waters from the nearshore regions of the East China Sea, that the process of aluminosilicate formation probably begins rapidly upon contact of detrital clays with seawater. Statistical analyses of dissolved Al-Si-H + relations in surface sediments indicate that the minerals forming in East China Sea sediments low in dissolved Fe are dioctahedral chlorites with an average composition EX 0.91Mg 0.77Al 5.0Si 2.7O 10(OH) 8 (where EX = exchangeable + 1 cation). This composition is also consistent with dissolved Al and Si measurements as a function of salinity in turbid overlying waters. Results suggest a dissolution—reprecipitation mechanism for clay mineral reconstitution. This mechanism can help to explain why different authigenic clays are found in different areas of the oceans. In the East China Sea the total amount of authigenic clays present must constitute a very minor fraction of the bottom sediments. Thus, the formation of these minerals has a relatively small impact upon dissolved Si distributions. Clay mineral reconstitution in nearshore regions may provide a mechanism for buffering sediments and overlying waters with respect to pH, as the composition of minerals formed should be a direct function of the H + activity in the surrounding environment.

Diagenesis and Mass Transfer in Sandstone-Shale Sequences: ABSTRACT

An analysis of diagenesis and mass transfer is made drawing on the literature and our work from the Brazilian shelf and Barbados. It is shown (although not unanticipated) that the initial sedimentary mineral composition is a major control of diagenetic products. For example, dioctahedral clay minerals, chlorite, and quartz characterize arkoses, whereas trioctahedral clays and zeolites are most commonly found in lithic sandstone. Dioctahedral smectite-rich shales exhibit the classical smectite/illite to illite burial pattern. However, mafic, trioctahedral clay-rich shales show a burial sequence of saponite to chlorite-rich phases with increasing burial depth. Other compositionally dependent reaction paths are also discussed. To assess mass transfer between shale and sandstone during burial, all major diagenetic pathways must be known for both rock types. A model for the Brazilian shelf sandstone-shale sequence is used as an example of quantification of mass transfer. Both sands and shales act as nearly isochemical systems; sandstones lose less than 2% K+ to shales, and gain less than 3% H2O, H+, and CO2 during burial diagenesis. It is shown using data from Barbados and the literature that burial diagenetic reactions are essentially irreversible, at least until the stage of weathering. Thus, these reactions can be used to assess the amount of overburden removed. Comparison of the diagenetically produced trend of illite/smectite compositions with depth in Barbados to trends produced in areas which have undergone only subsidence (e.g., Gulf Coast) suggests that about 3,300 to 9,800 ft (1,000 to 3,000 m) of overburden has been removed in Barbados. The irreversible and nearly isochemical nature of burial diagenetic reactions places constraints on the role of diagenesis in the sedimentary rock cycle. An attempt is made to quantify the global important of these reactions in the rock cycle. End_of_Article - Last_Page 508------------

Cation distribution, sheet thickness, and O-OH space in trioctahedral chlorites - an X-ray and infrared study.

One dimensional refinement and infrared OH band investigation have been made on five orthochlorites of the Mg–Fe series and on two Mg-leptochlorites with substitution of 2Al for 3Mg. The results indicate that the leptochlorites have cation vacancies in the interlayer sheet. Octahedral Al is concentrated in the interlayer sheet in every sample, but considerable amounts of Al are contained also in the 2: 1 octahedral sheet in the Al- and/or Fe-rich chlorites, which suggests a relatively narrow layer charge range in chlorites. The variation of cation composition of the tetrahedral and octahedral sheets results in variation of the sheet thickness and the interlayer O–OH space: with increasing tetrahedral Al (generally octahedral Al also increases), the two octahedral sheet thicknesses and the O–OH space decrease, but the tetrahedral sheet thickness increases; larger Fe2+ content brings about thicker octahedral and thinner tetrahedral sheets and smaller O–OH space.The O–OH space, which primarily determines the d(001) spacing, is concluded to be controlled by both the surplus negative charge of 2 : 1 layer surface oxygens and the interlayer octahedral cations; the former is caused by the tetrahedral Al substitution for Si and is affected also by the 2 : 1 octahedral cations. The OH bands and tetrahedral ordering of amesite and the O–OH spaces of dioctahedral chlorites and of some 1 : 1 layer silicates are discussed along with those of trioctahedral chlorites.

Calcretes of Olduvai Gorge and the Ndolanya Beds of northern Tanzania

ABSTRACTPedogenic calcretes are closely associated with Pliocene to Holocene wind‐worked deposits of volcanic ash in the Olduvai and Ndolanya Beds of northern Tanzania. The typical profile with calcrete consists of an unconsolidated sediment layer, an underlying laminar calcrete, and a lowermost massive calcrete. The laminar calcrete is a relatively pure limestone, whereas massive calcrete is aeolian tuff cemented and replaced by calcite. An Olduvai calcrete profile can develop to a mature stage in only a few thousand years. Carbonatite ash was the dominant source for most of the calcite in the calcretes.Replacement was a major process in formation of the massive calcretes, and oolitic textures have resulted from micrite replacing pelletoid clay coatings around sand grains. Phillipsite and possible other zeolites were extensively replaced in the massive calcretes. Replacement of clay by micrite in the Olduvai calcretes is accompanied by dissolution or leaching of phengitic illite and the formation of clay approaching the composition of halloysite or kaolinite. In the upper calcrete of the Ndolanya Beds, montmorillonite was altered to a kaolinite‐type mineral and to dioctahedral chlorite. Authigenic dolomite, zeolite, and dawsonite in the Olduvai calcretes probably received at least some of their components from replaced materials.

Lithium, a preliminary survey of its mineral occurrence in flint clay and related rock types in the United States

Maximum concentrations of lithium found in samples of flint clay and associated rocks of Pennsylvanian age in different States, in parts per million (ppm), are: Missouri, 5100; Pennsylvania-Maryland, 2100; Kentucky, 890; Ohio, 660; Alabama, 750; and Illinois, 160. Lithium-bearing kaolin deposits are distributed in the Coastal Plain province from New Jersey to Texas, and one occurs in Idaho; maximum lithium concentrations in samples from these deposits range from 64 to 180 ppm. The maximum concentration found in the Arkansas bauxite region is 460 ppm and that in flint clay in Colorado is 370 ppm. Samples from areas other than Pennsylvania, Maryland, Kentucky and Missouri are relatively few in number, represent mostly commercially valuable clays, and represent only a part of the refractory clay deposits in the United States. Data are not available on the clays associated with these deposits that may be unusable because they contain too much lithium as well as other deleterious elements. In both Pennsylvania and Missouri, lithium contents vary regionally between districts and locally between deposits.In samples containing more than 2000 ppm lithium, the lithium occurs in a dioctahedral chlorite mineral very similar to cookeite, which previously has not been recognized in sedimentary clays. The associated clays consist chiefly of well-crystallized kaolinite. The dioctahedral chlorite, however, seems to be most abundant where diaspore and boehmite occur along with the kaolinite. Barium, chromium, copper, phosphorus and strontium are present in some samples in amounts of several hundred pans per million or more, and may contribute to the failure of some clays to perform satisfactorily in firing tests.Lithium-rich clays could serve as a significant lithium resource in the very distant future. Clays that contain as much as 1% lithium may be common enough in Missouri or in Pennsylvania to be produced as a by-product to help support benefication costs for refractory clays. Sufficient amounts of lithium-rich clay may be found in deposits that have been explored, found unsatisfactory for normal refractory uses, and not developed. The lithium-rich clay in some deposits presently being worked may be worth stockpiling for eventual use.

Lithium-Bearing Tosudite

AbstractLithium-bearing tosudite was found from a brittle clayey part of the Tooho “roseki” deposit, Aichi Prefecture, Japan. The chemical composition of the Li bearing tosudite was estimated as SiO2 41·60%, A12O3 36·40%, Fe2O3 1·82%, MgO 0·29%, CaO 0·38%, Li2O 1·04%, Na2O 0·14%, K2O 0·38%, H2O+ 11·12% and H2O− 6·87% from the chemical composition of a specimen with associated impurities. The Li-bearing tosudite has the regularly interstratified structure of montmorillonite and dioctahedral chlorite in which Li is present in a gibbsite sheet as shown in the structural formula of interlayer cations K0·16, Na0·09, Ca0.13 + 9·60 H2O; gibbsite sheet Li1·36, Mg0·14, Fe0·45, Al3·59 (OH)12·00; silicate layer Al8·00 (Si13·60, Al2·40) O40·00 (OH)8·00. The 29·48 Å reflection series of the Li-bearing tosudite moves to 31·3 Å after ethylene glycol treatment and to 23·3 Å on heating to 500°C for 1 hr.

USE OF THE FIELDES AND PERROTT SODIUM FLUORIDE TEST TO DISTINGUISH THE B HORIZONS OF PODZOLS IN THE FIELD

The Fields and Perrott test, originally devised as a test for allophane, has been shown to give a positive test with soil materials having reactive Al(OH)x. This includes the Bf horizon of Podzols. In the test, a drop of saturated NaF solution is added to approximately 10 mg of soil on a spot test plate. After 2 min, the pH of the suspension, as measured with narrow range pH paper, divided a variety of B horizons into two groups. The Bf horizons gave pH values above 10.3 whereas Bm, Bg or Bt horizons all yielded pH values below 10.2 with this field test. The C horizons of a number of Podzols yielded a variety of pH values but the values were all low in the Ae and high in the B horizons. This grouping was found to be a funtion of the content of oxalate-extractable Al. Ground gibbsite, amorphous Al(OH)3, allophane, synthetic dioctahedral chlorite and Bf horizons which had greater than 1% oxalate-extractable Al yielded pH values in 1 M NaF solution of 11.0 or higher. Therefore, the Fieldes and Perrott test cannot be considered as a specific test for allophane.