Quartz Layers Research Articles

Characterization of the effects of embedded quartz layer on wear rates in abrasive wear

Understanding how the wear environment and the history of the wear surfaces affect wear and wear rates is extremely important in mineral processing and mining applications. Through this, the lifetime expectations of wear parts can be estimated more precisely in wear environments with constantly changing abrasive media. Certain mineral combinations can increase wear rates extensively compared to some others. The economical effects of unnecessary down-times are significant. In this study, the effects of embedded quartz layer on wear rates were investigated. Hard metals, metal matrix composites, and several types of steels were studied to find differences in their wear behavior. Running-in of the specimens was performed using quartz or granite abrasives to create surfaces with and without embedded quartz. Only granite was used as an abrasive in the actual wear tests. For low-hardness materials (<400 HV), the quartz running-in increased the wear rates in the actual wear tests, whereas for medium-hardness materials (400–800 HV) the wear rates were decreased. When the hardness of the tested material was higher than the hardness of quartz, the selection of running-in abrasive did not have an effect on the further wear rate. Characteristics of the embedded quartz layers on different substrates were further determined by scanning electron microscopy.

Evolution of ultrasonic velocity and dynamic elastic moduli with shear strain in granular layers

Ultrasonic wave transmission has been used to investigate processes that influence frictional strength, strain localization, fabric development, porosity evolution, and friction constitutive properties in granular materials under a wide range of conditions. We present results from a novel technique using ultrasonic wave propagation to observe the evolution of elastic properties during shear in laboratory experiments conducted at stresses applicable to tectonic faults in Earth’s crust. Elastic properties were measured continuously during loading, compaction, and subsequent shear using piezoelectric transducers fixed within shear forcing blocks in the double-direct-shear configuration. We report high-fidelity measurements of elastic wave properties for normal stresses up to 20 MPa and shear strains up to 500 % in layers of granular quartz, smectite clay, and a quartz-clay mixture. Layers were 0.1–1 cm thick and had nominal contact area of \(5 \mathrm{cm} \!\times \! 5 \mathrm{cm}\). We investigate relationships among frictional strength, granular layer thickness, and ultrasonic wave velocity and amplitude as a function of shear strain and normal stress. For layers of granular quartz, P-wave velocity and amplitude decrease by 20–70 % after a shear strain of 0.5. We find that P-wave velocity increases upon application of shear load for layers of pure clay and for the quartz-clay mixture. The P-wave amplitude of pure clay and quart-clay mixtures first decreases by \(\sim \)50 and 30 %, respectively, and then increases with additional shear strain. Changes in P-wave speed and wave amplitude result from changes in grain contact stiffness, crack density and disruption of granular force chains. Our data indicate that sample dilation and shear localization influence acoustic velocity and amplitude during granular shear.

Ecological characterization of soil-inhabiting and hypolithic soil crusts within the Knersvlakte, South Africa

Within the Knersvlakte, cyanobacteria occur hypolithically underneath translucent quartz stones in areas with quartz pavement and, outside pavement areas, they are soil-inhabiting within the uppermost millimeters of the soil. Both habitats were characterized in terms of biomass and growth patterns of cyanobacteria. Long-term microclimatic conditions were determined. Biomass of organisms within both habitats was determined by means of chlorophyll analyses. A transect approach was used to determine the frequency of hypolithic growth depending on the size, weight, and embedding depth of the quartz pebbles. Organisms were identified by means of microscopic analyses of the samples. Microclimatic conditions within both habitats, i.e., temperature, light intensity, air humidity, and soil moisture, were recorded bi-hourly from September 23, 2004 through September 7, 2006. The biomass of hypolithic and soil-inhabiting crusts was almost identical, 88 vs. 86 mg Chla/m2 and 136 vs. 134 mg Chla+b/m2. Within the quartz fields, 46.8% of the surface area was covered by quartz stones with 69% of translucent quartz stones colonized by hypolithic cyanobacteria and algae. Colonized quartz stones were significantly thicker, heavier, and more deeply embedded in the soil than uncolonized ones. Whereas the annual mean temperature on top of quartz stones was nearly identical to that underneath thin and thick quartz stones, daily temperature amplitudes were largest on the stone surface (up to 48.1K), compared to the hypolithic habitats (up to 39.4K). Light intensity in the hypolithic habitat was between 15 and 30% of the ambient light intensity during daytime. Water condensation in the absence of rain occurred during 50% of the nights on the quartz stone surface, but only during 34% of the nights on the soil surface during winter months within 1 year. Soil moisture beneath quartz layers was greater and less variable than beneath soil-inhabiting crusts. In spite of the large differences in the microclimatic conditions, both habitats seem to be similarly well suited for cyanobacterial growth, resulting in equal biomass values but some differences in taxonomic composition.

Visible Channeled Spectra of a Multilayer Wood Filter

ABSTRACT The transmission factor of multilayer Wood filters containing quartz and rutile layers was simulated in order to avoid the experimental trials for obtaining optical filters with predicted transmission. The main refractive indices of uniaxial crystals—quartz and rutile—were interferometrically determined and Cauchy constants were obtained by simulation. The transmission factor of optical devices consisting of quartz and rutile layers was simulated using the Maple Program.

Micro- and nano-textural evidence of Ti(–Ca–Fe) mobility during fluid–rock interactions in carbonaceous lawsonite-bearing rocks from New Zealand

Understanding the mobility of chemical elements during fluid–rock interactions is critical to assess the geochemical evolution of a rock undergoing burial and metamorphism and, more generally, to constrain the geochemical budget of the subduction factory. In particular, determining the behavior and mobility of Ti in aqueous fluids constitutes a great challenge that is still under scrutiny. Here, we study plant fossils preserved in blueschist metasedimentary rocks from the Marybank Formation (New Zealand). Using scanning and transmission electron microscopies (SEM and TEM), we show that the carbonaceous material (CM) composing the fossils contains abundant nano-inclusions of Ti- and Fe-oxides. These nanocrystals are mainly anatase, rutile, and Fe–Ti oxides. The mineral composition observed within the fossils is significantly different from that detected in the surrounding rock matrix. We propose that Ti and Fe might have been mobilized by the alteration of a detrital Ti–Fe-rich protolith during an early diagenetic event under acidic and reducing conditions. Aqueous fluids rich in organic ligands released by the degradation of organic matter may have been involved. Moreover, using mass balance and petrological observations, we show that the contrasted mineralogy between the rock matrix and the fossil CM might be the consequence of the chemical isolation of fossil CM during the prograde path of the rock. Such an isolation results from the early formation of quartz and Fe-rich phyllosilicate layers enclosing the fossil as characterized by SEM and TEM investigations. Overall, this study shows that investigating minerals associated with CM down to the nanometer scale in metamorphic rocks can provide a precious record of early prograde geochemical conditions.

Development of a micro-flame ionization detector using a diffusion flame

A micro-flame ionization detector (micro-FID) design is presented that is targeted for use in a portable gas sensor. Our micro-FID is based on a diffusion flame and features a folded flame structure that is more sensitive than a counter-flow flame designs. Unlike conventional FIDs that use a premixed or open diffusion flame, an air–hydrogen diffusion flame is employed and tested in an encapsulated structure of Quartz–Macor–Quartz layers. Diffusion flames are generally known to be more controllable and stable than premixed flames, where the stability of the micro-FID plays an important role for portable gas sensors. Various channel designs for oxidant and fuel flows meeting with different angles at the burner cavity are tested to obtain a stable flame and high output sensitivity over methane test samples. To verify the empirically designed microchannel, we simulate the temperature distribution in the microchannel by using computational fluid dynamics (CFD) software. To gauge the sensitivity of the device, the collected electric charges per mole (C/mol) is calculated and taken as a reference value of ionization efficiency. The result of the folded flame design is 1.959×10−2C/mol for methane that is about 34 times higher than the result using a counter-flow flame, which is 5.73×10−4C/mol for methane, while one of the commercial macro FIDs’ is 10−1C/mol. This result shows that the micro-FID using the folded flame structure has higher ionization efficiency with less leakage of the analytes than of the classical counter-flow flame design.

Origin of iron oxide spherules in the banded iron formation of the Bababudan Group, Dharwar Craton, Southern India

The banded iron formation of the Bababudan Group (Western Dharwar Craton, India) is composed of millimetric to centimetric alternating quartz and grey to red Fe-oxide bands. Major phases are quartz and martite (hematized magnetite) with minor Fe-sulfides and Ca–Mg–Fe-carbonates. Micrometric Fe-oxide spherules fill cavities in discontinuous micrometric layers of Fe-oxides that occur in the massive quartz layers and at the interface of massive Fe-oxide and quartz layers. The spherules are composed of micrometric radial plates of hematite intergrown with nanometric magnetite. These spherules contain carbonaceous matter (CM) with nanometric Fe-particles and have low N contents (∼900ppm; CM1). The spherule formation is attributed to a low temperature hydrothermal process (150–200°C) at around 2.52Ga, possibly favored by the presence of CM. These hydrothermal fluids dissolved diagenetic interstitial sulfides or carbonates creating cavities which, provided space for the spherule precipitation. Carbonaceous matter of semi-anthracite maturity is encapsulated in quartz grains adjacent to the Fe-oxide spherules (CM2) and it is thus concluded that CM1 and CM2 are most likely contemporaneous and of the same origin, either incorporated at the time of BIF formation or during the hydrothermal event at 2.52Ga from the underlying phyllitised black shales. Carbonaceous matter (CM3) was also found around the Fe-oxide spherules and the martite grains. CM3 has much higher N contents (>5000ppm), is of a lower maturity than CM1 and CM2, and is related to weathering, which is also indicated by the presence of goethite and kaolinite. The δ13C of all CMs varies from −19.4 to −24.7‰, similar to values measured in the underlying phyllitised black shales and likely reflect denitrifying microbial activity.

Restraint Effect of Filaments on Applied Voltage in Atmospheric Pressure Glow Discharge

In this study, argon and nitrogen were used as the discharge gases in radio-frequency (RF: 13.56 MHz) powered dielectric barrier atmospheric plasma. It was noticed that in single dielectric barrier discharge (DBD) with nitrogen as the discharge gas, or in argon plasma with a high applied power, micro-filament channels were easily formed. The channels in these two kinds of discharge were both constrictive on the bare metallic electrode and expansive on the opposite electrode covered with a quartz layer. The number of micro-channels was increased along with the input power, which caused the change in the I—V curve shape, i.e., the current kept increasing and the voltage fluctuated within a confined range. With double dielectric layers, however, no micro-channels appeared in the ICCD images, and the I—V curve demonstrated a totally different shape. It was assumed that micro-filaments exhibited a restraining effect on the discharge voltage. The mechanism of this restraining effect was explored in this work.

Preliminary Investigation of Permeation Profiles of Selected Head-Space Urine Volatiles (2-Heptanone, n-Octanal) Using IMS

The late location of entrapped victims in collapsed buildings is the main reason of high mortality during urban search and rescue (USaR) operations after natural or man-made disasters. Consequently, an effort is currently being made to develop proper rescue searching tools that could improve the early location of trapped casualties. In this context, the knowledge of human scent profile and its behavior in the disaster environment is crucial. The main goal of this study was to investigate the suitability of the ion mobility spectrometry (IMS) for the quantitative monitoring of specific urine-borne volatile members of human scent interacting with the materials of collapsed dwellings. For this purpose, an ion mobility spectrometer with β-radiation source (63Ni) and an in-house made filling chamber mimicking the entrapment scene were employed. In preliminary experiments, quartz sand was used as imitating debris material. The experimental setup was used to investigate the permeation properties of two very promising urine-borne species, 2-heptanone and n-octanal, under the influence of two crucial operational factors; the size of quartz grain and the quartz layer thickness. 2-heptanone was found to penetrate through quartz layer by approximately a factor 4 faster than n-octanal. The twofold and threefold increase of quartz sand thickness lengthened the permeation times on average three and seven times for n-octanal, and three and five times for 2-heptanone. The presented experimental setup can be considered as a useful tool suitable for investigating the interactions of urine markers with the debris materials in the entrapment scene. However, further investigations involving different debris materials (e.g. concrete, brick, cement, wood, plastic, glass) and other urine-borne species are necessary, prior selecting a set of volatile organic compounds (VOCs) that will support the early location method of entrapped victims.

Untangling galvanic and passivation phenomena induced by sulfide minerals on precious metal leaching using a new packed-bed electrochemical cyanidation reactor

Because permanent galvanic contacts between gold rotating disc electrodes and slurried sulfide-rich ores are uneasy to achieve, the standard gold rotating disc electrode/slurry cyanidation arrangement has a tendency to inflate overly the importance of passivation phenomena over the corrective trend of galvanic interactions inherently present within the ore grains. A new packed-bed electrochemical reactor (PBER) was thus developed and tested to decouple and quantify the individual contributions of passivation phenomena (PP) and galvanic interactions (GI) on precious metal (gold and silver, PM) leaching rates during the cyanidation of sulfide-rich ores. The PBER was filled with homogenized mixtures of minerals (pyrite, chalcopyrite, sphalerite, chalcocite, galena, stibnite, and industrial ore), gold and silver powders, which were arranged as electrically isolated sulfide-quartz segregated bilayer(s) with permanent (inter)particle–particle electrical contacts among all constituents in each layer. Implantation of PM powders successively in the quartz layer and then in the sulfide layer, enabled PP and GI to be singled out and quantified separately for each sulfide. Galvanic interactions were found to ameliorate, to various degrees, the leaching of PM. Locating the PM powders in the quartz layer emphasized the negative impact of PP of the sulfide layer on Au and Ag dissolution, except for galena which enhanced gold leaching kinetics. Galvanic interactions due to pyrite, chalcopyrite and an industrial ore were so positive that they largely outweighed the negative impact of PM passivation. The galvanic current measured between Au/Ag electrode and each of the above minerals confirmed the positive effect of GI on gold leaching rate. In close agreement with PM recoveries, stronger galvanic currents were measured for Au-pyrite, Au-chalcopyrite and Au-industrial ore galvanic couples in comparison to those for Au-sphalerite, Au-chalcocite and Au-stibnite.

Magnetoelectric behavior of ferrimagnetic BixCo2−xMnO4 (x=0, 0.1 and 0.3) thin films

Thin films of BixCo2−xMnO4 (x=0, 0.1 and 0.3) were grown on quartz, LaAlO3 (LAO) and YBa2Cu3O7 (YBCO) buffer layer coated LAO substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD) and Raman scattering measurements showed that the thin films exhibit single phase polycrystalline cubic spinel structure on all the substrates. Near edge X-ray absorption fine structure (NEXAFS) studies confirmed the octahedral occupancy of the substituted Bi3+ ions. Temperature dependent zero-field cooled (ZFC) magnetization measurements show the ferrimagnetic (FM) behavior (TC∼186K) and magnetization undergoes a crossover from positive to negative, owing to the opposite contributions of magnetic moments from Co and Mn ions. A weak ferroelectric property exhibited by the films above room temperature was evidenced through the capacitance–voltage (C–V) and dielectric measurements. Magnetoelectric coupling was found to be maximum just below FM-TC.

Swelling Characteristics of Shales and Their Dispersion in Drilling Muds II

The Tuns and Opuks shales are essentially kaolinitic with subordinate amounts of quartz, illite, and mixed layer clays. The total clay content of the shales varies from 55 to 92% with an average of 76%. The degree of reactivity in terms of their CEC is low and about 12 m.eq/100 mg on the average. The number of samples was, however, too small to be more useful. The high temperature/pressure assessment of the mud systems has revealed that the barite weighted SynTeq mud is more stable thermally and of better viscosity, gel strength, and load-bearing capacity than the other mud systems investigated. The secondarily viscosified Petrofree has some potential but is of low thermal resistance. It is concluded that the SynTeq mud system is generally a better drilling fluid for rocks in the Niger Delta than either Petrofree or KCL Polymer. The SynTeq is, therefore, recommended for adoption in the oil production company drilling operations. It has been re-emphasized as part of our recommendations that new guidelines for the close monitoring of drilling fluids supplied by mud companies and those actually used in the field (during drilling) be put in place.

Genesis of lateritic iron ore from banded iron-formation in the Capanema mine (Minas Gerais, Brazil)

Lateritic weathering of metamorphosed Proterozoic banded iron-formation (BIF), locally named itabirite in Brazil, produced large deposits of iron ore. At the Capanema iron-ore mine in the Quadrilatero Ferrifero in Minas Gerais state (southeast Brazil), the BIF is a bedded metasedimentary rock composed essentially of layers of hematite/kenomagnetite alternating with layers of quartz. The BIF is cut by dolerite dykes. The lateritic weathering of itabirite in wet tropical conditions resulted in a well-developed weathering mantle, with a specific succession of horizons of different chemical, mineralogical and textural compositions capped by a ferruginous duricrust or canga. The lack of alumina in the itabirite and the intense leaching of silica inhibited the formation of clay minerals. However, some alumina (from the weathered dolerite) is incorporated in secondary minerals. The process of alternating dissolution and reprecipitation of Fe and Al oxides and oxy-hydroxides controls the lateritic weathering. Eight different types of goethite (I–VIII) and three types of hematite (I–III) were identified based on texture, derivation and chemistry, related to five transformation fronts that include desilication, oxides dissolution, cementation, duricrust and erosion. Mass balance of the weathering column indicates varying iron redistribution (as goethite and hematite) through the profile, with an absolute enrichment of aluminium, locally derived from weathered dolerite. This alumina appears to act as an accelerant in the lateritisation process.

Two-dimensional numerical modeling of 90Sr transport in an unsaturated Chinese loess under artificial sprinkling

90Sr is a fission byproduct of uranium and plutonium, and it presents a major health problem in the environment. A field test on the transport of various radionuclides including 90Sr in an unsaturated Chinese loess was conducted under artificial rain conditions from July 1997 to August 2000. The vertical concentration distribution of 90Sr displayed an unusual profile of double concentration peaks, which were separated by a thin (0.7 cm) source layer. In order to interpret the double-peak concentration profile, the transport of 3H and 90Sr in the unsaturated Chinese loess under artificial sprinkling conditions was simulated using WATERM, a numerical code for simulating flow field, and NESOR, also a numerical code but for simulating nuclide migration. The models were able to adequately simulate the double-peak concentration profile. The observation suggested that the fine arenaceous quartz layer, though 0.7 cm thick, formed a capillary barrier together with the local loess, which prevented water from penetrating. A significant discrepancy was observed between the model-fitted distribution coefficient ( K d) of 90Sr and that determined from independent laboratory experiments, which can be attributed to a number of factors such as the capillary barrier effect, solution-to-solid ratio and soil water content. Therefore, when the model is used for predictive purposes where K d is used as an input parameter, K d must be determined under well controlled conditions by taking into account these factors as well as the heterogeneity in the field.

Fracture Modes in Curved Brittle Layers Subject to Concentrated Cyclic Loading in Liquid Environments.

Damage response of brittle curved structures subject to cyclic Hertzian indentation was investigated. Specimens were fabricated by bisecting cylindrical quartz glass hollow tubes. The resulting hemi-cylindrical glass shells were bonded internally and at the edges to polymeric supporting structures and loaded axially in water on the outer circumference with a spherical tungsten carbide indenter. Critical loads and number of cycles to initiate and propagate near-contact cone cracks and far-field flexure radial cracks to failure were recorded. Flat quartz glass plates on polymer substrates were tested as a control group. Our findings showed that cone cracks form at lower loads, and can propagate through the quartz layer to the quartz/polymer interface at lower number of cycles, in the curved specimens relative to their flat counterparts. Flexural radial cracks require a higher load to initiate in the curved specimens relative to flat structures. These radial cracks can propagate rapidly to the margins, the flat edges of the bisecting plane, under cyclic loading at relatively low loads, owing to mechanical fatigue and a greater spatial range of tensile stresses in curved structures.

The Akilia Controversy: field, structural and geochronological evidence questions interpretations of &gt;3.8 Ga life in SW Greenland

Abstract: Field relations, structure and geochronology demonstrate that controversial rocks on Akilia, SW Greenland, cannot host evidence of Earth's oldest life. Mafic–ultramafic gneiss that contains a layer of quartz–amphibole–pyroxene gneiss, a few metres thick, with purported biogenic graphite is not cross-cut by the protoliths of &gt;3.82–3.65 Ga tonalitic gneiss. The contact between these gneisses is tectonic so their relative ages are unknown. Multiple episodes of intrusion and deformation in the tonalitic gneiss preceded the earliest deformation fabrics and structures seen in the mafic–ultramafic gneiss. Although previously interpreted as a volcano-sedimentary stratigraphy, the mafic–ultramafic gneiss displays no evidence of such an origin, and could be partly or wholly derived from igneous intrusions. Existing geochronology indicates that the mafic–ultramafic and qtz–am–px gneisses have ages &lt;3.67 Ga. Metamorphic zircon in the qtz–am–px gneiss grew at c . 2.68 Ga during late Archaean high-grade events that complicate any protolith interpretation. U–Pb dating of apatite from a variety of rocks on Akilia shows that this mineral crystallized, or possibly recrystallized, at c . 1.75 Ga and it thus provides no indication of an early Archaean age for any associated graphite, regardless of whether or not the latter is biogenic. Supplementary material: Ion microprobe U–Pb analytical methods and isotope data tables are available at http://www.geolsoc.org.uk/SUP18333 .

Witherite (BaCO3)/α-Quartz Epitaxial Nucleation and Growth: Experimental Findings and Theoretical Implications on Biomineralization

Witherite (BaCO3) crystals have been synthesized by mixing BaCl2·2H2O and NaHCO3 aqueous solutions; their growth morphology is characterized by single and twinned individuals both [001] elongated and limited by {110} prism and {hhl} bipyramids. When quartz single crystals are used as substrates, heterogeneous nucleation of witherite occurs onto the {1010}, {1012}, and {0112} forms of quartz and {001} witherite lamellae grow along the [100], [001], and [121] directions of quartz. This witherite/quartz three-dimensional epitaxy is the first evidence that two-dimensional epitaxial layers of quartz can form as well on witherite nucleating from aqueous solutions containing Na-metasilicate. As it is known, nano-polycrystalline structures, the “silica biomorphs”, are precipitated from such solutions: this implies a very high nucleation frequency of witherite. We propose that this is caused by the lowering of the specific surface energy of witherite for the two-dimensional localized adsorption of silica chains.

Sub-micron parallel laser direct-write

We have developed a modified laser induced forward transfer (LIFT) technique which allows for the parallel deposition of hundreds of sub-micron features. The approach utilizes a self-assembled monolayer of monodisperse polystyrene microspheres as the focusing element. A monolayer of close-packed microspheres is formed on top of an ultra-thin quartz support (25 μm thick), and a metallic thin film is then deposited on the underside of the quartz. This approach is different from previous parallel microsphere-assisted LIFT experiments that required the deposition of metal directly onto the surface of the periodic microsphere structure. For this study, an 800 nm, 130 fs laser pulse was directed toward the microsphere layer to focus the incident laser beam through the thin quartz layer to the quartz–metal interface. At this interface, a portion of the thin metal film was ablated directly below each microsphere, resulting in an array of holes in the thin metal film. The metal removed from the film was patterned onto a receiving substrate to form an array of discrete deposits. In some cases, a two layer thin film was utilized resulting in the forward transfer of bilayer metal features. The holes and deposited features were characterized using scanning electron microscopy, atomic force microscopy, and scanning Auger electron spectroscopy. The diameter of the holes (0.5–5 μm) as well as the diameter (0.9–5 μm) and quality of the deposited metallic features were modulated by varying the sphere size, incident laser energy, and material composition.

Highly oriented GaN films grown on ZnO buffer layer over quartz substrates by reactive sputtering of GaAs target

Polycrystalline GaN films were deposited on quartz and ZnO buffer layers over quartz by reactive sputtering of a GaAs target in 100% nitrogen at 550 °C and 700 °C. Micro-structural investigations of the films were carried out using high resolution X-ray diffraction, atomic force microscopy and Raman spectroscopy. GaN films deposited on ZnO buffer layers exhibit strongly preferred (0002) orientation of crystallites. In particular, the film deposited at 700 °C on ZnO buffer layer over amorphous quartz substrate showed large crystallite size, both along and perpendicular to growth direction, strong and nearly complete c-axis orientation of crystallites with tilt of ~ 2.5° and low value of micro-strain ~ 2 × 10 − 3 . The significant improvement in crystallinity and orientation of crystallites in the GaN film is attributed to the presence of the ZnO buffer layer on quartz substrate and its small lattice mismatch (1.8%) with GaN.

Biological structures in Archean and lower Proterozoic rocks of the Kursk Magnetic Anomaly and Kola Peninsula

The integral duration of the Archean and Proterozoic eonothems approximates 4 Ga. The corresponding sediments of that time interval, which constitutes approximately 85% of the Earth’s history, are poorly characterized by signs of biological activity. Such a feature provided grounds for most researchers to neglect the influence of biological processes on sedimentation during that time. Nevertheless, some authors [2, 3] report solid evidence in favor of direct participation of living organisms in the formation of some rocks, confirming inferences by V.I. Vernadsky who believed that both the sedimentary and granite shells of the Earth represent products of past biospheres [1]. The formation of the Earth’s hydrosphere (approximately 4.4 Ga ago) and atmosphere (at first, oxygenfree, although not reducing [7]) was an important prerequisite for the appearance of life and, simultaneously, for the commencement of sedimentation. It is thought that the chemical composition of the Archean and Early Proterozoic atmosphere and hydrosphere differed sharply from that in the recent and Phanerozoic epochs [8]. It was oxygen-free and characterized by high contents of carbon dioxide, which influenced processes of hypergenesis. The chemical weathering during the Archean and Early Proterozoic was more intense than in subsequent epochs. Nevertheless, significant quantities of pelitic material, in addition to dissolved components of weathered rocks, should have been transported to sedimentation basins. Along with dissolved compounds of K, Na, Ca, Mg, and other elements, clayey particles of colloidal sizes should have been dispersed through the entire basin, preventing the formation of relatively pure (with respect to chemical and mineral compositions) beds of quartz, iron oxides, organic carbon, and other minerals and their associations. In fact, these rocks are highly differentiated as exemplified by jaspilite sequences. In our opinion, this fact provides logical grounds for the assumption that biological activity was a determining factor in the formation of quartz in most Archean and Lower Proterozoic pararocks (gneisses and jaspilites). Indeed, only living organisms can extract and accumulate various chemical components, which are frequently characterized by background concentrations, from the surrounding medium. The rocks constituting Archean‐Lower Proterozoic metamorphic complexes in the study regions experienced significant alterations and transformations through all the stages of catagenesis, metagenesis, and several phases of metamorphism. Based on investigations of siliceous rocks [4] genetically related to the metasomatic replacement of calcium carbonate in chalky rocks by silica, we hoped to define some kinds of biological traces using electron microscope methods, although we did not know what the traces should look like. Our work was based on the assumption of a primary biogenic carbonate or biogenic opal composition of quartz layers.