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Fossilized wood belongs to the most exciting, however, rarely studied objects in nature. Several kinds of petrified wood with different combinations of minerals have been studied: apatite – calcite; calcite – pyrite; hematite – gypsum wood; quartz - goethite; goethite – calcite woods, from different countries and estimated as old in the time range of 1.8–306 MA. The samples cover nearly the whole time of tree existence on the Earth. The application of synchrotron radiation for X-ray microdiffraction analysis of petrified wood is presented and compared to elemental (electron microprobe) and molecular (micro Raman) analyses with the use of table-top instruments. The analysis of preserved cells permineralized with two minerals allows tracing both the structure of cell walls and the remains of ancient organic matter. Lignin is most often met among the remains of the primary organic matter and is clearly observed in all kinds of wood, except the apatite-calcite one. The Eh-pH diagrams tailored to each combination of minerals with organic matter allow to estimate the original conditions of mineralization and give the indications for the potential biomimetic synthesis.

Gorontalo area is part of the arc volcano - plutonic North Sulawesi predominantly volcanic rocks and intrusif rock Eocene to Quaternary. The tectonic position makes the Gorontalo area of natural resource mining prospects both metallic and non metallic minerals. One of them is a non-metal potential of petrified wood. The purpose of this study to analyze the condition of geomorphology, lithology, stratgraphy, and determine the nature of the physical characteristics of petrified wood in order to formulate feasibility as gemstones. The method used qualitative and quantitative results of the field survey which is then compiled the results of the laboratory. Field analysis in the form of geological mapping, sampling and documentation of geological data. The laboratory analysis conducted mineralogical and geochemistry analysis in the form of X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF). Dissemination of research results, the petrified wood in Tohupo River and Molannihu River. Petrified wood found in fluvial and alluvial sediment in tuffaceous sandstone layer with two types of insitu and transported. Results of laboratory analysis both mineralogy and gochemistry indicates that the mineral constituent of petrified wood are Quartz (SiO 2 ) with good quality so worty as a gemstone because of its aesthetic, translucent and hardness 7 Mohs Scale.

Measuring density of silicified wood and determining weight loss after 450°C heating provides useful data for interpreting the process of permineralization. These simple gravimetric methods do not replace X-ray diffraction, electron microscopy, polarized light microscopy, Raman spectroscopy, and other specialized techniques for studying fossil wood, but they can be performed rapidly, and require minimal laboratory facilities. Woods mineralized with opal have densities of 1.9–2.1 g/cm3, compared to 2.3–2.6 g/cm3 for wood mineralized with chalcedony or quartz. Weight loss after 450°C heating, commonly described as “loss on ignition” can be used to roughly estimate the % of original organic matter that remains in chalcedony or quartz-mineralized wood, using the density of extant taxa for comparison. For opalized wood, 450°C weight loss mostly represents dehydration of the hydrous silica. Data from specimens from 20 localities reveal two characteristics: 1) silicified woods typically consist either of opal or chalcedony/quartz, not an intermediate mixture of the two silica polymorphs; 2) the percentage of organic matter that remains after petrifaction is usually very small.

The best-known and most-studied petrified wood specimens are those that are mineralized with polymorphs of silica: opal-A, opal-C, chalcedony, and quartz. Less familiar are fossil woods preserved with non-silica minerals. This report reviews discoveries of woods mineralized with calcium carbonate, calcium phosphate, various iron and copper minerals, manganese oxide, fluorite, barite, natrolite, and smectite clay. Regardless of composition, the processes of mineralization involve the same factors: availability of dissolved elements, pH, Eh, and burial temperature. Permeability of the wood and anatomical features also plays important roles in determining mineralization. When precipitation occurs in several episodes, fossil wood may have complex mineralogy.

Late Tertiary fossil woods from the state of Nevada provide an opportunity for observing the mineralization sequences that cause buried wood to become permineralized. Oligocene and Miocene caldera basins contain abundant petrified wood that ranges in composition from incipient silicification to complete permineralization. Examination of specimens from 21 localities reveals that the petrifaction sequence can follow multiple pathways. Fossil wood specimens from a single stratum may have different mineralization, silicification may vary even within a single specimen. Despite these variations, several trends are evident. Features in Nevada specimens suggest that two fundamental processes are involved: early mineralization of cell walls, and later silica deposition in lumina, vessels, and rot pockets from groundwater that permeated these open spaces. The process of open-space filling may be analogous to the genesis of geodes and veins, where multiple episodes of hydrothermal precipitation may produce opal, chalcedony, and quartz as deposits within a single cavity. Silica polymorphs may coexist as primary precipitates, or they may originate from solid-state transformation of a single parent material. Relic lepisphere textures observed in some chalcedony wood specimens are evidence of opal→chalcedony transition. In Nevada, specimens that contain crystalline quartz, this mineral appears to have been formed by direct precipitation in open spaces, not from recrystallization of chalcedony. Opal-A has seldom been reported in fossil wood, but this amorphous material is fairly common in Nevada specimens.

Fascination with petrified wood has stimulated interest in understanding the process of natural petrifaction. Early attempts of modeling natural petrifaction in the laboratory have been limited to mimicking incipient permineralization resulting in the creation of silica casts of pore spaces and inner cell walls. Silica lithomorphs produced through artificial silicification provided a possible avenue for studying microstructure of wood. More recently artificial petrifaction is motivated by the goal of creating advanced ceramic materials for engineering applications. The concept of using wood as a biotemplate has led to the creation of porous ceramics by cell wall replacement. To some extent artificial and natural petrifaction processes are comparable; although, some of the materials and procedures used in the laboratory are not found in nature. Research focused on the composition and structure of fossil wood from different-aged deposits is compared with research focused on the development of wood-templated porous ceramics. Differences and similarities in the pathways of natural silicification and creation of biomorphous ceramics are discussed. The comparison between artificial and natural silicification highlights the particular significance of the degree to which (de)lignification is needed for silica permeation.

Petrified wood has traditionally been divided into two categories based on preservation processes: permineralization (where tissues are entombed within a mineral-filled matrix) and replacement (where organic anatomical features have been replicated by inorganic materials). New analytical evidence suggests that for most petrified wood, permineralization and replacement are not independent processes; instead, both processes may occur contemporaneously during diagenesis. Infiltration of mineral-bearing groundwater may initially cause permineralization of cellular tissues, but the wood is undergoing gradual degradation. The degree of anatomical preservation thus depends on the relative rates of mineral precipitation and tissue destruction. Rapid rates of mineralization under relatively mild Eh and pH conditions favor the preservation of organic matter. These conditions appear to be more common for calcium carbonate deposition than for silicification, based on observations of fossil woods from many localities. Because of these preservational complexities, “mineralization” and “mineralized” are more accurate as general descriptive terms than “permineralization” and “permineralized”.

An extensive fossil forest discovered in 2010 on private property in central Colorado, USA, has not previously been described in scientific literature. Horizontal partial logs originated as fluvially transported driftwood. A preliminary study of petrified wood specimens reveals evidence of a complex mineralization sequence that involved multiple episodes of mineral deposition, combined with diagenetic transformation of silica minerals. Specimens from two logs have opalized cell walls. However, minerals filling the cell interiors of these specimens vary. Vessel lumina are filled with chalcedony or crystalline quartz; tracheid lumina may contain opal or chalcedony. Specimens from 5 other logs contain quartz/chalcedony, but relict textures suggest cell walls were originally mineralized with opal that was later converted to microcrystalline silica. Pyrite, calcite, and iron oxides were observed as minor constituents in some specimens, providing additional evidence that fossilization occurred in multiple stages, with temporal and spatial variations in physical and chemical conditions causing episodic precipitation of various minerals within the buried wood. Trace element analyses suggest that Fe is the main source of fossil wood color.

The research on chemical composition and microstructure of petrified wood has scarcely been reported in China and abroad, and the study about micro-mechanical characteristics has not been carried out. In this paper, the domestic and foreign research progress was summarized at the same time, and the crystal orientation in the cell wall of Pinus tabulaeformis petrified wood was measured according to the method of wood’s MFA using x-ray diffraction techniques, while micro-mechanical characteristics were further studied using nanoindentation. The results showed that silica crystals in petrified wood cell wall were arranged from 22.19 to 25.98 ° in accordance with the micro fibril angle. The micro-mechanical characteristics of silica crystals in different locations inside the petrified wood were different; the modulus and hardness of silica crystals in the lumen region were 89.86 and 9.33 GPa, but 63.07 and 5.20 GPa in the cell wall region. The difference of hardness and modulus of two parts regional were 44.34 and 27.30 %, respectively; this result was supported by A. Kuczumow’s study, which showed the variability of the secondary electron signal of Si could be even over 30 %, the easiest way to explain it was by claiming that the porosity is much increased.

In fossil specimens, measurements of the natural isotopic ratio (129)I/I may provide a method to estimate the age of sample. The motivation for measuring the isotopic composition ((129)I/I) of petrified wood samples collected from Austria was to check this feasibility. Alkaline fusion together with anion exchange was used to extract iodine from the sample. Typical sample size for this study was 10-90 g. An atomic ratio as low as 10(-14) was determined using accelerator mass spectrometry (AMS). Uranium concentrations measured by instrumental neutron activation analysis (INAA) and α-spectrometry were found to be less than 3 mg kg(-1), therefore the contribution from fissiogenic (129)I was small and an estimation of ages was based on the decrease of the initial ratio (due to decay of the cosmogenic (129)I in a closed system) after subtraction of the fissiogenic (129)I. The value of the prenuclear ratio is crucial for the use of the (129)I system for dating purposes in the terrestrial environment. From the preanthropogenic (initial) ratio of 1.5 × 10(-12) of the hydrosphere and the results of the present study for the samples from Altenburg (1.05 × 10(-12)) and Fuerwald (6.16 × 10(-13)), respective ages of 8 ± 2.2 and 20.2 ± 2.2 million years were derived. Since samples were collected from a stratum deposited in the Upper Oligocene/Ergerien period (~25-30 million years ago), it can be concluded that these isotopic ratios do not show ages but an elapsed time since fossil wood was isolated from mineral rich water. Paleontological investigation shows that samples from Altenburg had mixed characteristics of old and modern Tertiary plants, thus an origin from a younger stratum re-sedimented with Oligocene cannot be excluded. However, the sample from Drasenhofen reflects that the (129)I/I system might not always be suitable for the dating of petrified wood sample due to fixation of anthropogenic (129)I into surface fractures.

Transitions in petrified wood samples from several Thailand–Myanmar sites included opal-A to opal-CT, opal-A to metastable β -crystobalite and reordered opal-CT → quartz. The moganite in the samples indicates a potential volcanic silica source for the wood petrifactions. Silica phase transitions evident under SEM include opal-A → opal-CT, opal-A → cuboid quartz (pseudocubic) and opal-CT → quartz. Certain stages of silica transformation and transition processes seem to overlap. Such overlapping results when lepisphere blades transform to the high crystallinity of prismatic quartz through a solid-state mechanism. The results provide some insights into the petrified wood genesis in the region. Thermal inputs into the silicification process may have pre-dated final burial of woods in flood deposits.

Three typical plant taxa from the fossil assemblage of the 290-million-year-old Chemnitz Petrified Forest (Zeisigwald Tuff Horizon, Leukersdorf Formation) were studied with regard to the microstructure of the petrifactions: samples of the tree fern Psaronius sp., the seed fern Medullosa stellata, and the gymnosperm Dadoxylon sp. The plant’s tissues are anatomically preserved by silica exhibiting different crystalline order and by other mineralisations. Specimens were studied by means of electron backscatter imaging and electron backscatter diffraction in a scanning electron microscope. The cell walls were largely preserved by quartz crystals, the cell lumina by cryptocrystalline silica. The former organisation and chemical composition of the vascular tissue are mirrored by varying grain formation and grain size. Results are discussed in terms of extant xylem cell wall organisation showing highly hydrophilic cellulose and hemicellulose cross-linked by hydrophobic lignin. The effect of polar and non-polar wood components on the precipitation of silica from aqueous solution and on the formation of crystals is convincing, and the reported results provide a better understanding of how silica replaced organic matter during the petrifaction process.

Fossil forests have world-wide distribution, commonly preserving mineralized wood that displays vivid hues and complex color patterns. However, the origin of petrified color has received little scientific attention. Color of silicified wood may be influenced by the presence of relict organic matter, but the most significant contribution comes from trace metals. This study reports quantitative analysis of trace metals in 35 silicified wood samples, determined using LA-ICP-MS spectrometry. The most important of these metals is Fe, which can produce a rainbow of hues depending on its abundance and oxidation state. Cr is the dominant colorant for bright green fossil wood from Arizona, USA and Zimbabwe, Africa. Complex color patterns result from the progressive nature of the fossilization process, which causes wood to have varying degrees of permeability during successive episodes of permineralization. These processes include simple diffusion, chromatographic separation, infiltration of groundwater along fractures and void spaces, and oxidation/reduction.

The crystallite size, microstrain, stacking disorder and moganite content of flint and other chert raw materials were studied by X-ray powder diffraction profile analysis. The broadening of the X-ray reflections of all microfibrous quartz varieties is due to both anisotropic small crystallite size and anisotropic microstrain. The microstructure varies for samples of different origin. The moganite content and the number of structural defects are higher in flint than in older chert and petrified wood. The X-ray diffraction pattern of the cortex of flint differs from that of the core material, whereas those of the patina and the unweathered interior of the rocks do not.

The fossil forest in the Camlidere-Celtikci-Gudul region of the province of Ankara in Turkey has a large number of petrified coniferous and oak tree remains. Petrification occurred in volcanic ashes and tuffs with permineralization, and Fe, Mg, Ca and Ni ions played important roles in the substitution of Si for C. However, the petrified wood samples are heterogeneous in colouration, weight, toughness, and durability, despite being obtained from the same source. Those features are very important for end-users because petrified woods, if cut and polished, are used widely as both decorative indoor tiles and gemstone objects, but heterogeneous materials suffer large wastage while they are being worked and used. Chemical analyses, specific gravity measurements, polarizing microscope studies, X-ray diffraction patterns, and scanning electron image evaluations were performed to classify and identify the homogenous material of the petrified woods relating to its physical and mineralogical characteristics. The different characteristics of the petrified wood samples are due to their varying inner structures, which depend on the replacement silica-building phases and their ratios, and silica particle sizes. Thin sections and XRD patterns revealed that petrified woods in the region were silicified by replacement with both chalcedonic quartz components, including chalcedony (length-fast quartz), moganite and orthorhombic -silica (length-slow quartz), and opalline quartz components including opal-CT and opal-C (length-slow quartz). The scanning electron microscope images were shown that the internal structures of the petrified woods consist of mostly submicron-sized (100–800 nm), and partially nano-sized (60–120 nm) silica-building particles. So, the petrified wood samples can be firstly classified into five main-groups based on their colourations and specific gravity values, then, into three sub-groups based on the principal chalcedonic and opalline quartz silica-building phases and related particle sizes, and also weighing, toughness, and durability. In the first group (samples 1, 2, and 3), the crystallinity gradation of the petrified woods can be classified as quasi-coarse crystalline because they include mainly chalcedony and moganite phases with 800–200 nm ranging in particle size. They are heavy, tough, and resistance as a material, as shown by specific gravity values of 2.60, 2.56, and 2.54, respectively. In the second group (sample 4), the crystallinity gradation of the petrified wood can be classified as quasi-fine crystalline because it includes mainly o -silica and moganite phases with 400–100 nm ranging in particle size. It is medium-heavy, semi-tough and quasi-resistance as a material, as shown by a specific gravity value of 2.42. In the third group (sample 5), the crystallinity gradation of the petrified wood can be classified as quasi-nano-crystalline because it includes mainly opal-CT and opal-C phases with 120–60 nm ranging in particle size. The material is slight, brittle, and weak as a material, as shown by a specific gravity value of 2.18. Ultimately, in the petrified wood found in the Camlidere-Celtikci-Gudul region of Ankara province in Turkey, it is revealed that samples 1, 2, and 3 represent flint and chalcedony quartz mineral species, samples 4 and 5 represent chalcedony and opal quartz mineral species.

Fine structure and tissue substitution by minerals were investigated in silicified woods from Madagascar and Indonesia by scanning electron microscopy and X-ray microanalysis. The silicified woods maintained the exterior morphology of once grown trees and showed typical inner structures of conifers. Radial planes of the silicified wood from Madagascar revealed tracheids as a major component of the axial system in the secondary xylem. Tracheids were mainly characterized by numerous bordered pits where a thickening in the middle (torus) was surrounded with the membrane (margo). The torus appeared to contrast with the fibrillar network of the margo. As a component of the axial system in the secondary phloem, sieve elements were found to have many sieve pores that were filled with seemingly crystalline materials. To correlate the colors of the silicified wood from Indonesia with elemental composition, energy-dispersive X-ray spectrometry was employed in this study. Silicon was present as a basic component of the silicified wood. Calcium and iron were detected from red-colored regions, whereas magnesium was found in blue-colored regions. These results suggest that tissues of silicified woods had been substituted by minerals over the past period, while retaining the inherent morphology of the tree species. Scanning electron microscopy and X-ray microanalysis could be applied to unravel structural details and composition of plant fossils in palaeobotany.

Dense propane has been used as a solvent for the continuous countercurrent extraction of base oil from waste lubricant oil. The aim of the work has been to identify the best processing conditions t...

Special kinds of petrified wood of complex structure were investigated. All the samples were composed of at least two different inorganic substances. The original cell structure was preserved in each case. The remnants of the original biological material were detected in some locations, especially in the cell walls. The complex inorganic structure was superimposed on the remnant organic network. The first inorganic component was located in the lumena (l.) of the cells while another one in the walls (w.) of the cells. The investigated arrangements were as follows: calcite (l.)—goethite–hematite (w.)—wood from Dunarobba, Italy; pyrite (l.)—calcite (w.)—wood from Łukow, Poland; goethite (l.)—silica (w.)—wood from Kwaczala, Poland. The inorganic composition was analysed and spatially located by the use of three spectral methods: electron microprobe, X-ray synchrotron-based microprobe, μ-PIXE microprobe. The accurate mappings presenting 2D distribution of the chemical species were presented for each case. Trace elements were detected and correlated with the distribution of the main elements. In addition, the identification of phases was done by the use of μ-Raman and μ-XRD techniques for selected and representative points. The possible mechanisms of the described arrangements are considered. The potential synthesis of similar structures and their possible applications are suggested.

The possibilities of examining patterned natural and mineralised biological objects, using X-ray synchrotron facilities, complemented by electron microprobe and optical analysis are reviewed. The objects under investigation include: petrified wood, speleothems, corals, shells of molluscs and remains of belemnites. All those objects have important information embedded in their patterned structure. Using microprobe type devices, one can disentangle the internal structure of the objects and reveal the hidden information. This information can be of great significance to climatic, geological, chronological, and ecological studies and specific examples in each category are shown, taken from our work and compared with the results of other authors where necessary. The added value of the X-ray and electron microprobe measurements in relation to the mass-spectrometric methods is shown for the specific cases. In addition, the results concern materials where organic and even biological material is combined with inorganic matter, like calcite, silica varieties and metal oxides. The investigation of such patterned objects as goethitized wood, composed of goethite, calcite and organic matter should therefore be of interest to materials scientists, synthesizing composite materials.

Three representative samples of petrified wood were investigated: wood from King George Island, Antarctica; wood from Bio-Bio province, middle Chile and wood from Łukow, Poland. Microdiffraction measurements of the Chilean and Łukow wood were made at LURE. Chilean and Antarctic samples were permineralised by silica material, but the share of undefined calcium silicates in construction of some intracellular locations in the latter sample was significant. In contrast, the wood from Łukow was replaced by calcite with a small presence of secondary silica. Linear scans were conducted using the X-ray microfluorescence beamlines in synchrotron devices in Orsay, France and Pohang, South Korea. The results were completed by the measurements of light elements with the use of electron microprobe. The list of major and minor constituents of all samples was established. The occurrence of such medium-Z elements as Fe, Zn, Cu and Ni was common in the samples. The samples of Chilean wood were more enriched in trace elements and minor amounts of As, La, Br and Cl were found in addition to the previously mentioned elements. Correlation of the trace element contents with the ring structure of the wood was detected. The annual ring, tissue and even cell details of the original wood were preserved by silica and calcite minerals and could be studied using the elemental mapping technique. Implications of the recent study for the material science are indicated.

The investigation of the interesting collection of the petrified wood from Bondyrz, Roztocze, south-eastern Poland, has been continued. Two kinds of microprobes such as electron microprobe from the Catholic University of Lublin and synchrotron-based X-ray microprobe from LURE, Orsay, were applied to detect the elements associated with the main component – silica and their spatial distribution and interrelations. The distribution of carbon in the petrified material has been established, which is important since that element is the main remains from the history of the trees. The carbon distribution was characteristic – it concentrated on a place of primordial dark wood. The distribution patterns of the other elements were either similar to that of carbon (Cu, Pb) or they concentrated in separate inclusions (Fe, Al, K, Na, Ca). The replicating mode of the original wood pattern in silica and carbon-containing material was explained. Some indications about the composition of the primordial petrifying solution, the rate of the petrifaction process and the recent coloration of the sample could be concluded from the compositional patterns of silica. The boundary between totally and partially petrified zones could be well observed.

Since the investigations on petrified wood performed so far have not proved the assumption that the ring structure is coupled to the changes in the crystalline form of silica, attention was paid to other possible reasons. Using small angle X-ray scattering methods we determined the Porod curves and pore size distributions for five different samples of petrified wood, of different origin. We observed clear porosity differences in different samples. In addition, the normal X-ray diffractometric measurements were carried out, which gave a totally uniform image of the crystallographic structure of all the samples. All of them were made of pure α-quartz. The differentiation of rings in dark and bright zones should be put down to the changes in porosity rather than to other factors. The pores seem to be much more concentrated in those ring locations, which correspond to the original dark wood positions in living wood.

Pieces of petrified wood from south-eastern Poland comprising one of the greatest European collections were investigated. The age of Miocene wood was estimated at 50 million years. Taxodioxylon sequoianum Gothan. was recognised as the dominating species among the preserved samples. Silica material, basic for the petrifaction processes, was investigated by synchrotron-based microfluorescence and microdiffraction. Different distribution patterns were determined after careful examination of linear scans and elemental maps: calcium, potassium and titanium were uniformly spread in the silica matrix while the iron content was concentrated in clear inclusions; other detected elements, as Cu, Zn, Cr, As were observed mainly in the form of inclusions. There was no difference in microdiffractograms for silica between the places of original dark and light wood. One could find little difference in diffraction patterns of samples with the elevated content of iron. In general, the diffraction patterns of silica from petrified wood could be associated with quartz patterns from 1998 JCPDS-International Centre for Diffraction Data.

Samples of petrified wood of different origins were analyzed by the use of the electron microprobe, capillary X-ray fluorescence microprobe, synchrotron capillary X-ray microprobe and optical microscope, applied in a microprobe manner. The main attention was given to the investigation of the ring structure of the petrified wood and the comparison of this with the ring structure of the living trees analyzed by much the same methods. The continuous X-radiation, applied in a microprobe manner, the distribution of the gray-scale representation of the secondary electron intensities and the characteristic X-ray signals, mainly from the light elements, were registered by the use of the electron microprobe method. The X-ray capillary microprobe detected the Rayleigh and Compton signals, scattered from microareas of the samples, and the characteristic X-ray signals, mainly from the heavier elements. In the synchrotron-based capillary microanalytical measurements, one of the most important results was achieved by the microprobe application of scattered synchrotron radiation. The emission and scattering results were supplemented by transmission measurements, where possible. All the methods proved to be complementary in the analysis of such periodic structures as tree rings. Both capillary microprobes were much more efficient in the detection of heavy elements and penetrated deeper than the traditional electron microprobe. Careful analysis of different signals indicated that some samples of petrified wood in the authors' possession, composed of silica of variable density, are the chemical negatives of the primordial living wood. This is the first such observation in the literature. Microdiffraction studies of the samples proved that polycrystalline α-quartz was the main matrix component of all these samples. The elemental analysis of the petrified wood gives important indications about the petrification processes. Comparison of the particular ring structure of the petrified wood with the ring structure of living trees shows great similarities. The widths of rings, density variations and density maxima are easily readable from the microanalysis of petrified wood. These parameters potentially can be exploited for the investigation of the biological, chemical, chronological and climatic information included in the fossilized tissues.

Field investigations of Middle Miocene fluviatile sediments in an open sand pit at Voervadsbro, Denmark suggest that the transformation processes of wood (lignification and petrifaction) depend on the permeability of the sediment. The petrifying agent in the wood is silica, which must have originated from weathering (and/or soil formation) of silicate minerals as the sediments have seen no history of volcanism. Petrographic investigations (by transmitted light microscopy and SEM) and X-ray diffraction have revealed the resultant of the petrifying agent to be quartz with a remarkably high crystallinity considering its age. The radial structures of the cell walls and the rim around the cell lumina-filling indicate that the first precipitation has been on the cell walls. The zonation of the quartz shows that its precipitation proceeded with interruptions, due to local differences in silica supply, seasonal changes and/or ground-water fluctuations.

The concentrations and distribution of radionuclides in a petrified wood forest in El-Qattamia have been determined using high-resolution gamma spectrometry to evaluate the environmental radioactivity. The mean activity concentrations of (238)U, (232)Th and (40)K were 65.26+/-12.99, 23.66+/-0.95 and 146.33+/-1.50 Bq kg(-1), respectively. Data of the soil samples show evidence of possible deposition and accumulation of (137)Cs. The mean activity concentration of (137)Cs in the soil samples was 4.37+/-0.16 Bq kg(-1) with a range of 0.00-35.70 Bq kg(-1). The measured activity concentration range of (137)Cs was compared with reported ranges in the literature from some of the other locations in the world. The radium-equivalent, dose rate in air and annual effective dose rate were evaluated. The mean activity concentrations of the gamma-ray emissions from radionuclides in El-Qattamia petrified wood forest region were relatively low.

Silicified stumps at Florissant Fossil Beds National Monument are subject to degradation from a variety of causes including freeze-thaw weathering. In the past, noninvasive measures have been taken to conserve selected fossils, including use of metal bands for reinforcement and construction of shelters. Our study had two goals. The first was to document the temperature and relative humidity to which petrified stumps are exposed at Florissant. The second was to conduct a preliminary examination of the feasibility of using consolidants and adhesives to reinforce fossil wood and reduce its susceptibility to weathering. Electronic data loggers were used to monitor temperature and relative humidity both internally and externally for one exposed and one sheltered fossil stump, and results indicated that over 289 days of the cold season there were 119 freeze-thaw events for the surface of the exposed stump and 95 events for the surface of the stump protected by a roof. Temperature and humidity variations were markedly lower for the subsurface sensors. Seven organosilicate formulations were field tested as consolidants on samples of petrified wood. Adhesives used to repair fractures included two polyvinyl butyral (PVB) formulations, two casein adhesives, and one epoxy. After eight months of exposure, fractures repaired with epoxy remained well bonded. Specimens repaired with PVB remained intact, but outer regions were visibly damaged, presumably from UV radiation. Of the two casein products that were tested, one had poor bond strength and the other was difficult to apply because of its low viscosity. Evaluating the effectiveness of organosilicate emulsions as consolidants to reduce weathering rates will

Among all the fossils, petrified wood belongs to the most impressive and most common of materials. Still, its study has not exceeded the purely phenomenological level. The recognition of the conserved structure of petrified wood seems to be of meaning for understanding the geological past, the complete carbon cycle inside the Earth, and the structure of potential new materials. The first ever published spatial distributions of the remains of the primordial organic material (lignin, cellulose, pectins) in the cells of permineralized wood, from Dunarobba (Central Italy), are presented here. They were collected using μ-Raman spectrometry. The composite nature of the petrified material (calcite located in the lumena of cells and goethite located in the cell walls) was confirmed by electron, proton, and X-ray microprobes. The structure of the cell walls was well preserved. The mineralization process was induced by the tracheidal water flow and was stopped after formation of pipe-like goethite shielding of the cell walls on the cellulose scaffolds. The chemical (Eh and pH ranges) and probable microbial conditions for such a pattern of mineralization were determined. We estimate that substantial amounts of the primordial organic matter were preserved in bodies of petrified wood on a global scale. The wood petrifaction process, if well understood, can be a basis for the production of “everlasting” organic–inorganic composite compounds.

Samples of different three-dimensionally preserved fossil plants ( Medullosa sp., Dadoxylon sp., Calamodendron striatum , Psaronius sp.) from the Lower Permian petrified forest of Chemnitz were examined with regard to their chemical composition and structural order. Raman spectroscopy and cathodoluminescence microscopy are shown to be powerful tools for such investigations. Silicified wood from Chemnitz–Hilbersdorf generally shows yellow cathodoluminescence (CL) of the cell walls and only weak yellowbrownish CL of the cell lumina. By time-resolved cathodoluminescence spectroscopy, a secondary mineralisation of hydrothermal origin was recognized. The latter is shown by short-lived blue CL at the cell walls extinguishing the yellow signal. Therefore, after the primary silicification step a secondary mineralisation step initiated by hydrothermal processes, seems to have taken place at probably slightly higher temperatures. The resulting silica matrix consists of phanerocrystalline and microcrystalline -quartz as well as microcrystalline moganite, both partially associated with iron oxides. Dadoxylon sp. is a prominent example for parallel permineralisation by -quartz and fluorspar, which is outstanding for the Chemnitz Petrified Forest. CL on this samples shows parallel silicification and fluoritisation, followed by infiltration of iron oxides. Permineralised samples show very low percentage of original organic remains. The seed fern Medullosa, for example, shows dispersed carbon, which is mainly restricted to the centres of the typical star-shaped vascular bundles. Raman spectroscopy revealed that these carbonaceous particles are of an anthracite structure. For experimental confirmation coal samples of different rank, especially anthracite from different geological times and localities, were studied by means of Raman spectroscopy. The remaining pith of the vascular bundles is white-coloured and consists of -quartz and moganite, whereas surrounding tracheides exhibit white and reddish coloured parts. The reddish parts, mainly found in the rays, additionally contain -Fe2O3 and Fe3O4 among the SiO2 polymorphs of -quartz and moganite. Sometimes iron oxides could have dominated permineralisation processes as the peak intensities of distinct parts of the samples suggest. © 2004 Elsevier B.V. All rights reserved.

MINERALOGY Tiger's eye is the popular name for gem-quality quartz-rich material composed of gold to brown fibrous bands that exhibit chatoyancy (lustrous color changes with an undulating narrow band of white light, like a cat's eye). Blue tiger's eye (also called hawk's eye) gets its blue color and chatoyancy from crocidolite, an asbestiform amphibole. In tiger's eye, the brown colors are derived from the hydrothermal alteration of the crocidolite to goethite. Both gems were thought to be produced by pseudomorphism, in which quartz replaces most of the crocidolite while retaining its fibrous structure (like petrified wood or mineralized fossils). After 125 years of this textbook explanation, Heaney and Fisher have determined that tiger's-eye is formed instead by a repetitive crack-seal mechanism. Host rock that contains crocidolite is fractured by stress and heat; silica-saturated fluids enter the crack; and, while crocidolite grows out from the host rock, columnar quartz grows around and between the crocidolite. Thus, tiger's eye records the structural and thermal path of the host rock and can be used to reconstruct tectonic events.— LR Geology 31 , 323 (2003).

Seventy-five woods of Australian origin have been examined by means of X-ray diffraction, optical and scanning electron microscopy, and differential thermal analysis. The silica is in one or other of the following forms: opal-A, opal-CT, chalcedony, quartz, quartz + chalcedony, opal + chalcedony. More than half of them consist of opal-CT or chalcedony. The results indicate that petrifaction by silica involves penetration of the wood via splits or checks, permeation of cell walls via a reticulated system of micropores, enlargement of the micropore system as cell wall components break down, and continuing deposition of silica ata rate and in a manner consistent with maintaining the dimensional stability of the wood. Deposition of silica in cell lumina and intercellular voids may be sometimes, but not always, a separate and later event. The final stages of lithification involve loss of water and perhaps transformation of one form of silica into another.

A mineralogical investigation by X-ray powder diffraction and optical, scanning, and transmission electron microscopy of partially weathered petrified wood in the Yegua Formation (Eocene) of east-central Texas revealed that microcrystalline quartz present in the unaltered petrified wood has been gradually dissolved and replaced by disordered silica polymorphs (mainly opal-CT) as a result of weathering. This replacement suggests that the reaction sequence: opal-A → opal-CT → quartz, which has been described elsewhere to occur during diagenetic alteration of petrified wood, is apparently reversed when the petrified wood is exposed to low-energy weathering conditions. The relatively high rate of dissolution of the quartz in the petrified wood appears to be related to its small crystallite size. The silica released by the dissolution of the quartz is subsequently reprecipitated as disordered cristobalite-tridymite (opal-CT) and poorly crystalline silica (opal-A) that, in turn, probably converts to opal-CT on aging. Opal-CT is the major silica phase in the completely altered powdery material enclosing the partially weathered petrified wood. The intermediate zone between the altered and unaltered zones contains both quartz and opal-CT.

In Tsuyazaki area, Fukuoka Prefecture, there spread Cretaceous granodiorites and Tertiary sediments, in which many kinds of zeolites occur as the veinlets with quartz or calcite and as the cementing materials of conglomerate. These zeolites were identified as heulandite, laumontite, leonhardite, stilbite and analcime by X-ray diffraction, and their chemical compositions were obtained by electron probe micro-analyser. Heulandite has a composition of Ca0 65 Na4 70 K0 74 Mg0 08 Al825 Si28 09 O72 · 22.87H2O and occurs as the cementing material of conglomerate. Stilbite has a composition of Ca1 9 Na6 16 K0 58 Mg0 04 Al9 74 Si26 03 O72· 27.47H2O and often occurs on the heulandite crystal. Leonhardite has a composition of Ca3 41 K0 42 Mg0 01 Al7 74 Si16 38 O48·13.96H2O and occurs as the veinlets with quartz. Analcime has a composition of Na0 94 Ca0 03 Al0 98 Si2 02 O6 0.99H2O and occurs as an idiomorphic crystal in the vug of sandstone in association with a petrified wood. Judging from their occurrences, it is thought that the zeolites found in Tsuyazaki area were formed by the hydrothermal process.

The mineralogy of thirty-three samples of silicified wood was examined by X-ray diffraction, and each sample was found to consist of one of the following: opal-A opal-CT or quartz. The correlation between ordering of the silica phases and sample age suggests that the opal-A opal-CT quartz conversion sequence occurs in much the same manner and at approximately the same rates as in biogenic siliceous marine sediments. In addition, a poorly crystalline clay phase (illite?) was identified in most of these samples. Groundwater leaching of volcanogenic sediments, commonly thought to be the silica source, may also provide aluminum and other cations that are deposited simultaneously in wood tissue; consequently, silica recrystallization may be accompanied by authigenic clay formation.

At the outset the author described in some detail the geographical aspect of the country. He then mentioned the temples and monuments which he had visited, particularly noting the rock-materials of which they were composed. Some of these buildings were entirely of alabaster, formed as a secondary deposit in the caverns which had been hollowed in the Tertiary limestone, while others were composed of the limestone or the granite of Assouan, or of the Nubian sandstone. He then gave an account of various geological phenomena observed by him. One group of beds on the opposite side of the Nile from Assouan seemed to be identical lithologically with our own Carboniferous rooks, with the Arran section of which they might be compared on account of the way in which they had been altered by the neighbouring granite. The general similarity was heightened by the occurrence of beds of ironstone and carbonaceous deposits, contained charred plant-remains. Another highly interesting section showed an intrusive boss of quartz surrounded by mica-schist. The occurrence of a large number of blocks of the petrified wood of an exogenous tree in the loose sand overlying the nummulitic limestone near Cairo was also described, while overlying the petrified forest was a bed of sand containing numerous beautifully-rounded water-worn pebbles, mostly of quartz. It was not easy to account for the origin of these pebbles, as the nearest rocks containing quartz, which Mr. Neilson had seen, lay something like 600 miles further south. On the surface of the desert This 250-word extract was created in the absence of an abstract

In the month of July 1885, the writer was asked to accompany a Chinese gentleman, proceeding from Shanghai, to visit certain deposits of copper-ore reported to be very rich and extensive, and occurring on some property up the Yangtse river. Specimens of the ore had been sent to Shanghai and were given to the writer for inspection. These consisted of mixed ore of copper of dark brown colour, being mostly impure oxides with a little unchanged sulphide permeated by streaks of carbonate. The mineral was very heavy, and showed by a rough test about 70 per cent. of metallic copper. The most interesting feature, however, was the external appearance of the pieces, one of which was intact as taken from the earth near the surface, showing a striking resemblance to the well-known form of petrified wood, and suggesting the possible association of organic agency in its origin. This peculiarity of course dispelled the first assumption of large veins, though adding to the interest of investigating the mineral source, which proved to be near the open Port of I-Chang, on the Yang-tse-Kiang, about 1000 miles from the sea. The country surrounding I-Chang, on the western border of the province of Hon-peh, is very mountainous, being on the confines of the extensive ranges through which the river Yang-tse-Kiang here emerges from its eastward course through the province of Setchuan. The low hills in the immediate vicinity of I-Chang are composed of reddish sandstone and conglomerate beds dipping very slightly to S.E.; but

Electron spin resonance (ESR) spectra of both organic and inorganic radicals in petrified woods have been studied for the assessment of age and burial condition. Young woods contain lignin radicals that produce a signal with a width of about 7 G at g=2.0036. Radical spectra of acetic acid (CH2COOH·) and of methyl (CH3·) with hyperfine structures were observed for petrified woods of the Miocene epoch. ESR signal at g=2.0025 similar to coal was observed for the black carbonated portion. The spectrum, similar to that of natural quartz, was observed for silicated petrified woods older than Miocene. It is concluded that a rough age estimation of petrified wood can be made with ESR.