Non-silicate Minerals Research Articles

A comprehensive and consistent mineral dissolution rate database: Part III: Non-silicate minerals including carbonate, sulfate, phosphate, halide, and oxy-hydroxide minerals

A comprehensive and consistent mineral dissolution rate database: Part III: Non-silicate minerals including carbonate, sulfate, phosphate, halide, and oxy-hydroxide minerals

Osteohistological analysis and preservation stage of Coendou magnus Lund, 1839 (Rodentia, Erethizontidae) fossils recovered at Toca da Barriguda Cave, Northeastern Brazil

Studies on taxonomy, taphonomy, and paleoecology have been conducted on fossils from carbonate caves, however, surveys detailing the fossilization processes and bone microstructure of specimens from caves are still scarce. Our paper provides an osteohistological analysis and X-ray diffraction of a fossil rib from the extinct South American porcupine Coendou magnus Lund. Our results allowed us to interpret that there was microstructural preservation and low replacement of the organic part of the bone by minerals present in the surrounding sediments, such as apatite and abundant non-silicate minerals in sedimentary rocks, characterizing preservation in an environment with poor weathering. Keywords: cave, X-ray diffraction, late Pleistocene, histology, porcupine.

An Overview on (LDHs)

Layered Double Hydroxides are inorganic solid minerals with brucite-like structures. They are non-silicate minerals seen in the soil very rare in amount [1]. LDHs have brucite-like layers with an excess positive charge on their surface. The excess charges are balanced by anions that are present in the interlayer. Generally, LDHs are also known as Hydrotalcite-like compounds because Hydrotalcite is one of the LDHs seen commonly in soil. Due to their higher anion exchange capacity, they are also known by the name anionic clay. In nature, they generally occur as a clay mineral, but sometimes as the metabolic by-product of micro-organisms. Even humans can manufacture it at a low cost of production.

A robust chemical weathering index for sediments containing authigenic and biogenic materials

Chemical weathering is an important process at Earth's surface. Given that the chemical composition of sediments reflects the weathering environment in which they were generated, this can provide insights into the intensity and style of weathering during the past. Weathering indices calculated from the whole-rock geochemical compositions of sedimentary rocks are widely used. However, these indices have limitations, such as contamination by non-silicate minerals. To develop a weathering index widely applicable to sedimentary rocks formed under various conditions, we used compositional data and multivariate statistics to analyse a dataset for igneous rocks and their weathering profiles. The chemical variations of the igneous rocks and weathering trends were independently extracted from the dataset, and a new weathering index (the robust weathering (RW) index) is proposed. The applicability of the RW index was assessed using saprolite profiles and zonal soils. We further applied the RW index to a carbonate-rich paleosol to test its use in studies of paleoclimate. The RW index is robust even for sediments containing a large amount of non-silicate materials, and thus enables comparison of the weathering intensity of a wide range of sedimentary rocks. Spatial–temporal reconstructions of paleo-weathering conditions will be improved by applying the RW index to terrestrial and marine sediments.

Mineral-Supported Photocatalysts: A Review of Materials, Mechanisms and Environmental Applications

Although they are of significant importance for environmental applications, the industrialization of photocatalytic techniques still faces many difficulties, and the most urgent concern is cost control. Natural minerals possess abundant chemical inertia and cost-efficiency, which is suitable for hybridizing with various effective photocatalysts. The use of natural minerals in photocatalytic systems can not only significantly decrease the pure photocatalyst dosage but can also produce a favorable synergistic effect between photocatalyst and mineral substrate. This review article discusses the current progress regarding the use of various mineral classes in photocatalytic applications. Owing to their unique structures, large surface area, and negatively charged surface, silicate minerals could enhance the adsorption capacity, reduce particle aggregation, and promote photogenerated electron-hole pair separation for hybrid photocatalysts. Moreover, controlling the morphology and structure properties of these materials could have a great influence on their light-harvesting ability and photocatalytic activity. Composed of silica and alumina or magnesia, some silicate minerals possess unique orderly organized porous or layered structures, which are proper templates to modify the photocatalyst framework. The non-silicate minerals (referred to carbonate and carbon-based minerals, sulfate, and sulfide minerals and other special minerals) can function not only as catalyst supports but also as photocatalysts after special modification due to their unique chemical formula and impurities. The dye-sensitized minerals, as another natural mineral application in photocatalysis, are proved to be superior photocatalysts for hydrogen evolution and wastewater treatment. This work aims to provide a complete research overview of the mineral-supported photocatalysts and summarizes the common synergistic effects between different mineral substrates and photocatalysts as well as to inspire more possibilities for natural mineral application in photocatalysis.

Mechanisms of Soil Organic Carbon Stabilization Via Complexation with Non-Silicate Minerals in a Loess Soil

Mechanisms of Soil Organic Carbon Stabilization Via Complexation with Non-Silicate Minerals in a Loess Soil

Sources identification and contamination assessment of heavy metals in soil of Middle Nile Delta, Egypt

Sedimentological and geochemical studies are integrated to determine the potential of heavy metals in the Middle Nile Delta soil. Four sources of trace elements were identified; a geogenic source includes Fe, Co, Cr, Ni and V, along with Ca that partly enhanced by anthropogenic input, and three dissimilar anthropogenic sources grouped the elements as follow; As, Pb, Zn Cu, Ba and P which derived mainly from industrial activities; Ba, Pb, Zn and Cu group is likely dispersed by traffic emissions, and P, As and Cu elements group which influenced by agrochemical application and drain water irrigation. The concentrations of studied elements increasing with decreasing the particle size. Moreover, two groups of mineral assemblages of soil are recognized; the first group deposited with one particle fraction and inherited from parent materials, The second one includes non-silicate minerals clasts, deposited with more than one fraction and most likely of anthropogenic source.

Evaluation of Nitric Acid Extraction of Elements from Soils and Sediments in Two watersheds in East Tennessee

ABSTRACTDetermining the total elemental concentrations of soils requires a total dissolution method, in which hydrofluoric acid (HF) is commonly used. However, this method is tedious and risky due to the dangerous reagent HF. This study compared a single acid extraction technique using a nitric acid (HNO3) extraction method to total dissolution (HF + microwave assisted aqua regia) for evaluating the total elemental concentrations in soils and sediments. The two methods were used to analyze the elemental content of soils and sediments from the Oostanaula Creek and Pond Creek watersheds in East Tennessee. Twenty-one elements (Al, Ba, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Nd, P, S, Si, Sr, Ti, V, Zn, and Zr) were subsequently measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The extraction efficiency for HNO3 relative to the total was compared and discussed. In general, HNO3 can extract the elements in absorbed phases and those residing in non-silicate minerals. Six elements (Ba, Co, Fe, Ca, Mn, and P) generated significant correlations between total and HNO3 in both OC and PC watersheds. Finally, the elements were grouped according to the interrelationships of their total elemental concentrations based on the dendrogram plots, suggesting their geochemical association in soils and sediment forming minerals.

Geology, Mineralogy and Geochemistry of the Oligocene Oolitic Iron Ore of the Continental Terminal Formation, Kandi Basin, North-East Benin

The Oligocene Continental Terminal Formation of the Kandi Basin contains high grades of iron mineralization (~56.72% Total Fe). The microscopic study under the polarized and reflected light showed that the iron ore consists of silicate minerals (quartz 50% and zircon 1%) and non-silicate minerals (goethite 30%, hematite 7%, magnetite 3%, pyrite 1%, chalcopyrite 1%, blende 3%, galena 3%, scheelite 1% and gold 2%). The X-rays fluorescence shows that the iron ore is characterized by various elements, such as Fe2O3 (57.91% to 91.33%), SiO2 (3.07% to 33.19%), aluminum (2.94% to 7.74%), vanadium (0.04% to 0.11%), phosphorus (0.79% to 2.29%) and sulfur (<0.3%). The deleterious elements grade is above the permissible limit in metallurgy (0.05% - 0.07% for phosphorus and 0.1% for sulfur). Their high grades indicate that the Kandi Basin iron ore characteristics are not favorable for steel manufacturing despite its good vanadium contents (0.04% to 0.11%). However, it could be used for the cast iron manufacture. Spectrometric analysis by atomic absorption confirms the presence of low-grade gold associated to the iron ore (from 0.006 to 0.015 ppm). The comparative study of discontinuous stratiform iron ore of the Kandi Basin with other oolitic iron ores in exploitation from other countries such as Brazil, Australia, China, Russia, Uganda and the United States shows that iron ore of the Kandi Basin can be mined despite its high silica content.

An assessment of the Ca weathering sources to surface waters on the Precambrian Shield in central Ontario

There is increasing concern over the negative ecological impacts caused by falling calcium (Ca) concentrations in lakes, particularly in central Ontario, Canada. Forecasting regional changes in lake Ca concentrations relies on accurate estimates of mineral weathering rates that are not widely available. In this study, bulk atmospheric deposition, surface water and soil chemistry along with 87Sr/86Sr isotope measurements were used to provide regional insight into weathering controls on Ca concentrations in lakes. Regionally, Ca concentrations in 90% of 129 lakes sampled in central Ontario were <0.1 mmol L−1 and the Ca/Sr ratio in lakes increased and the K/Sr ratio decreased with increasing Sr concentration, which is indicative of greater Ca sources from calcite or apatite in the higher Ca lakes. Significant relationships between 87Sr/86Sr ratios and Ca/Sr rations in dilute acid (0.1 M HCl) soil extracts are also indicative of the presence of trace amounts of calcite or apatite in surficial soils. Within the low (<0.7 mmol L−1) Ca lakes, defined in this study that are considered most at risk from falling Ca concentrations, 87Sr/86Sr ratios fell within the range observed in weak acid soil extracts and were also significantly related to Ca/Na and K/Sr ratios in surface waters. There were large inconsistencies however, between Ca/Na ratios and Ca/Sr in surface waters and soil acid extracts that suggest differences in 87Sr/86Sr ratios in surface waters of the low Ca lakes do not simply reflect differences in Ca derived from non-silicate minerals in surficial soils and that that Ca sources from deeper soil or bedrock are also important contributors to surface water Ca in these low Ca lakes.

Volcano–hydrothermal system of Ebeko volcano, Paramushir, Kuril Islands: Geochemistry and solute fluxes of magmatic chlorine and sulfur

Ebeko volcano at the northern part of Paramushir Island in the Kuril island arc produces frequent phreatic eruptions and relatively strong fumarolic activity at the summit area ~1000m above sea level (asl). The fumaroles are characterized by low-temperature, HCl- and S-rich gas and numerous hyper-acid pools (pH<1) without drains. At ~550m asl, in the Yurieva stream canyon, many hot (up to 87°C) springs discharge ultra-acidic (pH1–2) SO4–Cl water into the stream and finally into the Sea of Okhotsk. During quiescent stages of degassing, these fumaroles emit 1000–2000t/d of water vapor, <20t/d of SO2 and <5t/d of HCl. The measurement of acidic hot Yurieva springs shows that the flux of Cl and S, 60–80t/d each, is independent on the volcanic activity in the last two decades. Such high flux of Cl is among the highest ever measured in a volcano–hydrothermal system. Oxygen and hydrogen isotopic composition of water and Cl concentration for Yurieva springs show an excellent positive correlation, indicating a mixing between meteoric water and magmatic vapor. In contrast, volcanic gas condensates of Ebeko fumaroles do not show a simple mixing trend but rather a complicated data suggesting evaporation of the acidic brine. Temperatures calculated from gas compositions and isotope data are similar, ranging from 150 to 250°C, which is consistent with the presence of a liquid aquifer below the Ebeko fumarolic fields. Saturation indices of non-silicate minerals suggest temperatures ranging from 150 to 200°C for Yurieva springs. Trace elements (including REE) and Sr isotope composition suggest congruent dissolution of the Ebeko volcanic rocks by acidic waters. Waters of Yurieva springs and waters of the summit thermal fields (including volcanic gas condensates) are different in Cl/SO4 ratios and isotopic compositions, suggesting complicated boiling–condensation–mixing processes.

Genesis of Si-rich carbonatites in Huanglongpu Mo deposit, Lesser Qinling orogen, China and significance for Mo mineralization

The Huanglongpu carbonatite-related Mo ore field is located in the Lesser Qinling Orogenic belt in the southern margin of the North China block. The ore field is composed of six deposits, Yuantou, Wengongling, Dashigou, Shijiawan, Taoyuan and Erdaohe, all of which are genetically related to carbonatite dykes except for the Shijiawan deposit which is associated with a granitic porphyry. The Yuantou carbonatite dykes intruded into Archean gneiss and other carbonatites emplaced into Mesoproterozoic volcanic and sediment rocks. The carbonatites are mainly composed of calcite and variable amounts of quartz and K-feldspar and minor molybdenite. Re–Os dating of molybdenite from the Yuantou carbonatite yields a weighted average age of 225.0±7.6Ma, consistent with the molybdenite age (221Ma) from the Dashigou deposit. The rocks are characterized by high heavy REE (HREE) contents and consistent flat REE distribution patterns with La/Ybcn ~1. Quartz in the carbonatites from Yuantou and Dashigou deposits shows consistent O isotopes (8.1–10.2‰) similar to the associated calcite (7.2–9.5‰). The quartz and associated K-feldspar contain lower Zr, Hf and higher HREE abundances and negligible Eu anomaly relative to those from the granite porphyry in Shijiawan. Both minerals are primary products in the carbonatitic liquid, and not captured from the wall-rocks or crustal-derived silicate magmas, or a hydrothermal origin. Thus, the Huanglongpu carbonatitic liquids were enriched in Si and Mo, which may be produced by intensely fractional crystallization of non-silicate minerals.

Coupling spatial geochemical and lithological information to distinguish silicate and non-silicate chemical weathering fluxes

Lithological maps have been proved to be a useful tool to evaluate regional and global matter fluxes from chemical weathering. However, lithological classes provide aggregated information of mineralogical, geochemical, sedimentary or diagenetic properties. Thus, using a limited number of lithological classes introduces by their definition a bias to the analysis of weathering fluxes, specifically in the case of multilithological catchments. Here it is shown that the coupling of geochemical with lithological information may help to better identify the sources of the weathering fluxes, using the example of dissolved Ca to better distinguish weathering rates of silicate and non-silicate minerals.

Chemical weathering rates of silicate-dominated lithological classes and associated liberation rates of phosphorus on the Japanese Archipelago—Implications for global scale analysis

Lithology is an important characteristic of the terrestrial surface, whose properties influence chemical weathering rates. Specifically non-silicate minerals may contribute significantly to the weathering derived fluxes from silicate-dominated lithological classes. The Japanese Archipelago consists of predominantly silicate-dominated lithologies with a high proportion of volcanics. However, the spatially explicit representation of chemical weathering rates remains difficult for such a large region, because many controlling factors on chemical weathering rates are correlated with each other. Due to the spatial heterogeneity of lithology, a multi-lithological model approach to estimate spatially explicit chemical weathering rates for unmonitored areas is applied here. To achieve this, hydrochemical data of 381 catchments are used to train a set of models, recognizing the contribution of a variety of proposed factors influencing chemical silicate rock weathering rates (CSRWR: cations plus dissolved silica flux). The monitored catchments cover ~44% of the Japanese Archipelago. Cation chemical weathering rates (excluding Si) are linearly correlated with CSRWR and show outliers if basic volcanics or pyroclastic flows are present due to increased silica release rates.Lithology and runoff are identified as the strongest predictors for chemical weathering rates. Temperature and gradient of slope are of less relevance for the regional scale prediction while further proposed factors like soil properties or land cover are not identified as major predictors. Latter findings are partly attributed to geodata quality, low variability of parameter values as well as spatial correlations of proposed controlling factors with lithology or runoff.The calculated average CSRWR of the Archipelago is ~25tkm−2a−1 and ranges from 5.9 to 107tkm−2a−1 in monitored catchments. Weathering rates per lithological class as a function of runoff can be grouped into three classes: a) pyroclastic flows showing the highest chemical weathering rates; b) alluvial deposits, mixed sediments and basic to intermediate volcanics with medium rates; and c) metamorphics, siliciclastic sediments, acid volcanics, acid plutonics and unconsolidated sediments (other than alluvial deposits), showing the lowest rates.The recognition of lithogenic sulfur would add 9.7% to CSRWR of considered catchments. Results suggest that the lithological classes acid volcanics and unconsolidated sediments contribute above average to the sulfur fluxes. Possible biases of this observation are discussed.The contribution of Ca-fluxes from non-silicate calcic minerals (named Ca-excess, Ca-fluxes in addition to silicate Ca-fluxes) is about 10% of the CSRWR on average and is attributed by a wide value range. The calculated ratio “Ca-excess to total Ca-fluxes” from chemical weathering averages around 62%, 75%, 56%, 83% and 84% for the lithological classes acid plutonics, metamorphics, siliciclastic sediments, mixed sediments and acid volcanics, respectively. This suggests a major Ca-contribution from non-silicate calcic minerals for these lithological classes.Phosphorus release from rocks due to chemical weathering is estimated to be between 1kg Pkm−2a−1 and 390kgPkm−2a−1. The P-release patterns in dependence of runoff per lithological class are different from CSRWRs due to differences of applied P-content in rocks. The identified spatial P-release patterns suggest that the consideration of dynamic and spatially resolved P-release rates by chemical weathering might improve ecosystem studies. Later findings may be of importance for analysing the influence of P-release from rocks on the climate system via ecosystem functioning on geological time scales. A first application of the P-release model to the global scale suggests an annual release of 1.6Mt P (13.8kgPkm−1a−1) by chemical weathering of silicate dominated lithological classes (excluding carbonate sedimentary rocks).

Diffusion in Carbonates, Fluorite, Sulfide Minerals, and Diamond

Research Article| January 01, 2010 Diffusion in Carbonates, Fluorite, Sulfide Minerals, and Diamond D.J. Cherniak D.J. Cherniak Department of Earth & Environmental Sciences, Rensselaer Polytechnic Institute Troy, New York 12180, U.S.A., chernd@rpi.edu Search for other works by this author on: GSW Google Scholar Reviews in Mineralogy and Geochemistry (2010) 72 (1): 871–897. https://doi.org/10.2138/rmg.2010.72.19 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D.J. Cherniak; Diffusion in Carbonates, Fluorite, Sulfide Minerals, and Diamond. Reviews in Mineralogy and Geochemistry 2010;; 72 (1): 871–897. doi: https://doi.org/10.2138/rmg.2010.72.19 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyReviews in Mineralogy and Geochemistry Search Advanced Search This chapter focuses on diffusion in non-silicate minerals that do not fall under any of the other chapter categories. This includes minerals that are not oxides (fluorite, sulfide minerals, diamond) and those, like the carbonates, that are not among the oxide minerals discussed in Chapter 17 of this volume (Van Orman and Crispin 2010). Although there are numerous minerals in these categories, limited diffusion data exist for many of them, so the primary phases that will be considered are carbonates, fluorite, diamond, and sulfide minerals. Carbonate minerals are major constituents of sediments and many sedimentary rocks. Fractionation of... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A survey of hybrid twins in non-silicate minerals

This article is the second part of the survey presenting a systematic crystallographic analysis of hybrid twins in minerals. Here we deal with silicate minerals and in particular the hybrid twins of allanite, augite, axinite, beryl, chloritoid, clinoenstatite, clinozoisite, cordierite, cummingtonite-grunerite, diopside-hedenbergite, enstatite-ferrosilite, epidote, forsterite-fayalite, johannsenite, natrolite, piemontite, pigeonite, protoenstatite, pumpellyite, pyroxmangite, quartz, titanite, spodumene, staurolite, topaz, tourmaline, tremolite-actinolite-ferroactinolite, tridymite. The comparison with the twin analysis of non-silicate minerals shows that the number of hybrid twins for non-silicates is higher than that of the silicates. This well agrees with the fact that the twin formation is favoured by the high symmetries of the close-packing topologies, typical of many non-silicates, especially oxides and simple sulphides, whereas the silicate structures are more complex and characterized by different degrees of polymerization of Si-O tetrahedra.

Combined approach for fractioning metal compounds in soils

A combined approach for fractioning metal compounds in soils on the basis of sequential and parallel extractions is proposed. This approach has been used to assess the group composition of Zn, Cu, and Pb compounds in an ordinary chernozem and its changes upon the soil contamination with metals. The contents of firmly and loosely bound metal compounds that are presumably fixed by the particular soil components (organic substances, carbonates, and silicate and nonsilicate minerals) have been determined.

A variabilidade de composição da apatita associada a carbonatitos

A apatita, um dos minerais não silicatados mais abundantes na crosta, é praticamente o único mineral de minério dos depósitos fosfáticos explotados no mundo. A fórmula estrutural simplificada da fluorapatita (espécie mais comum) é Ca1O(PO4)6 F2. Muitos substituintes podem ser encontrados, em todos os sítios cristaloquimicos, em apatita de todos os ambientes geológicos e mesmo dos materiais apatiticos orgânicos e sintéticos. São discutidos aqui principalmente os casos naturais e inorgânicos associados a carbonatitos. A ocupação do sítio aniônico monovalente dá as denominações principais atualmente aceitas oficialmente para as espécies dentro do grupo da apatita: fluorapatita, hidroxiapatita e clorapatita. Entre os substituintes do cálcio, podem ser destacados os elementos terras raras e elementos com interesse ambiental, como o cádmio, que pode ser incorporado aos fertilizantes, resultando em problemas de contaminação. Havendo duas posições distintas para o cálcio e seus substituintes na estrutura da apatita, vários dos estudos mais recentes exploram este aspecto, mostrando influências de todo um conjunto de fatores que interagem com as características de cada elemento na preferência de ocupação do sítio Ca1 ou Ca2. Entre os ânions substituintes para o fosfato, destaca-se o carbonato, cuja entrada provoca modificações estruturais e exige mecanismos de compensação de cargas, como substituições acopladas nos sítios catiônico e aniônico monovalente para manutenção da neutralidade da estrutura, ou mesmo criação de vacâncias estruturais. Esta questão ainda é polêmica e vem sendo abordada há muitas décadas, sendo considerada fundamental na questão da compreensão da variação da solubilidade, reatividade, cristalinidade e estabilidade térmica. O ânion carbonato também pode entrar no sítio do flúor, embora raramente.

Landed XRD/XRF analysis of prime targets in the search for past or present Martian life.

Mars landers seeking evidence for past or present life will be guided by information from orbital mapping and from previous surface exploration. Several target options have been proposed, including sites that may harbor extant life and sites most likely to preserve evidence of past life These sites have specific mineralogic characteristics. Extant life might be gathered around the sinters and associated mineral deposits of rare active fumaroles, or held within brine pockets and inclusions in a few evaporite-mineral deposits. Possibilities for fossilization include deltaic and lake-bottom sediments of once-flooded craters, sinters formed by ancient hot-spring deposits, and the carbonate deposits associated with some evaporite systems. However, the highly varied mineralogy of fossil occurrences on Earth leads to the inference that Mars, an equally complex planet, could host a broad variety of potential fossilizing deposits. The abundance of volcanic systems on Mars and evidence for close associations between volcanism and water release suggest possibilities of organism entrapment and mineralization in volcaniclastic deposits, as found in some instances on Earth. Thus the targets being considered for exploration include a wide variety of unique deposits that would be characterized by silica or various nonsilicate minerals. Beyond these "special" deposits and in the most general case, an ability to distinguish mineralized from uncemented volcanic detritus may be the key to success in finding possible fossil-bearing authigenic mineralogies. A prototype miniaturized X ray diffraction/X ray fluorescence (XRD/XRF) instrument has been evaluated with silica, carbonate, and sulfate minerals and with a basalt, to examine the capabilities of this tool in mineralogic and petrologic exploration for exobiological goals. This instrument. CHEMIN (chemical and mineralogical analyzer), is based on an innovative low-power X ray tube, transmission geometry, and CCD collection and discrimination of diffracted and fluoresced X rays. The ability to accumulate and integrate the entire circumference of each complete Debye diffraction ring compensates for poor powder preparations, as might be produced by robotic sampling systems. With CHEMIN, a wide range of minerals can be uniquely identified. Using Rietveld analysis of the XRD results, mineral quantification is also possible. Expanded capabilities in phase analysis and constrained data solutions using quantitative XRD and XRF are within reach.

Hydrogen in α-Alumina and Water Softening of Polycrystals and of Sapphire Between 600°C and 1000°C

Trace hydrogen impurities influence the physical and chemical properties of silicate minerals. Hydrogen defects reduce the plastic yield strengths of quartz and olivine (Kronenberg, 1994; Kohlstedt et al., 1996) and they increase rates of oxygen diffusion and A1/Si exchange in feldspars (Farver and Yund, 1990). Hydrogen impurities may similarly affect the properties of oxides and other non-silicate minerals, as suggested by early studies by Heuer et al. (1971), who reported water weakening of fine-grained (2 gm) aluminum oxide at 1200~ and 1400 MPa confining pressure. In this study, we revisit the mechanical properties of ~-A1203 in the presence of water, and examine the uptake of hydrogen impurities by single crystals and polycrystals at temperatures of 600-900~ and PH20 1500 MPa.