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The products of cement–asbestos treated in air at 1100 °C were characterized by a multi-methodological approach to determine: (i) the effective deactivation of harmful asbestos fibers; (ii) the mineralogy and microstructure of the inert product and its possible use as a secondary raw material (SRM); and (iii) any potential health hazard of the SRM. For this purpose, energy-dispersive X-ray fluorescence spectrometry (EDXRF), X-ray powder diffraction (XRPD), scanning, and transmission electron microscopy (SEM and TEM) analyses were performed. The powdered SRM was also analyzed by dynamic laser scattering and solution leaching experiments, to determine grain size distribution and possible elements release. Our results confirm the deactivation of crocidolite and chrysotile asbestos fibers, but at the same time evidence a significant fraction of nanoparticles in the SRM and some critical releases of SO42–, F– and Cr6+ in solution. Both the nanoparticle fraction and the critical elemental release may pose human health concern and adversely affect potential applications of the SRM. Strategies to control the grain size distribution through adjusted thermal treatment conditions and microwave-assisted grinding operations are discussed. Possible routes to safely reuse the SRM are indicated.

Nowadays, asbestos-containing wastes (ACW) still represent an important environmental problem and a severe health hazard due to the well know pulmonary diseases derived from asbestos fibers inhalation. Except for a very few cases, ACW are currently confined in controlled landfills, giving rise to increasingly high amounts of still hazardous wastes. A promising alternative to landfill confinement is represented by ACW inertization, but the high cost of the inertization processes so far proposed by the scientific community have hampered the creation of actually operative plants. In this paper, we explore the possibility to use an innovative process that ensures the obtainment of asbestos-free inert material in an exceptionally short processing time, thus greatly reducing cost-related problems. The efficacy of the inertization process has been verified through accurate mineralogical investigations on both chrysotile and crocidolite de-activated fibres, through X-ray diffraction, scanning and transmission electron microscopy. Overall mineralogical, microstructural and granulometric characteristics of the inert bulk material suggest that it could be successfully re-used as a secondary raw material in ceramic industries. This innovative inertization procedure could therefore provide an effective and economically sustainable solution for ACW management.

Nowadays, asbestos-containing wastes (ACW) still represent an important environmental problem and a severe health hazard due to the well know pulmonary diseases derived from asbestos fibers inhalation. Except for a very few cases, ACW are currently confined in controlled landfills, giving rise to increasingly high amounts of still hazardous wastes. A promising alternative to landfill confinement is represented by ACW inertization, but the high cost of the inertization processes so far proposed by the scientific community have hampered the creation of actually operative plants. In this paper, we explore the possibility to use an innovative process that ensures the obtainment of asbestos-free inert material in an exceptionally short processing time, thus greatly reducing cost-related problems. The efficacy of the inertization process has been verified through accurate mineralogical investigations on both chrysotile and crocidolite de-activated fibres, through X-ray diffraction, scanning and transmission electron microscopy. Overall mineralogical, microstructural and granulometric characteristics of the inert bulk material suggest that it could be successfully re-used as a secondary raw material in ceramic industries. This innovative inertization procedure could therefore provide an effective and economically sustainable solution for ACW management.

Fibrous chrysotile has been the most commonly applied asbestos mineral in a range of technical applications. However, it is toxic and carcinogenic upon inhalation. The chemical reactivity of chrysotile fiber surfaces contributes to its adverse health effects by catalyzing the formation of highly reactive hydroxyl radicals (HO•) from H2O2. In this Haber-Weiss cycle, Fe on the fiber surface acts as a catalyst: Fe3+ decomposes H2O2 to reductants that reduce surface Fe3+ to Fe2+, which is back-oxidized by H2O2 (Fenton-oxidation) to yield HO•. Chrysotile contains three structural Fe species: ferrous and ferric octahedral Fe and ferric tetrahedral Fe (Fe3+tet). Also, external Fe may adsorb or precipitate onto fiber surfaces. The goal of this study was to identify the Fe species on chrysotile surfaces that catalyze H2O2 decomposition and HO• generation.

Accelerated carbonation of ultramafic mine tailings has the potential to offset CO2 emissions produced by mining ores from Cu-Ni-platinum group element, podiform chromite, diamondiferous kimberlite, and historical chrysotile deposits. Implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore-processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures. Here, column experiments were designed to trial two geochemical treatments that address these criteria: direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation (10% CO2 in N2); and repeated heap leaching of ultramafic tailings with dilute sulphuric acid. In the first experiment, rapid carbonation of brucite [Mg(OH)2] is reported in the presence of 10% CO2 gas within tailings sampled from the Woodsreef chrysotile mine, New South Wales, Australia. Within four weeks, a doubling is observed of the amount of CO2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field. Reactive transport modelling (MIN3P) is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years. Finally, synchrotron X-ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals (Fe, Ni, Mn, Co, Cr) become highly concentrated within secondary Fe (hydr)oxide minerals at the pH neutralisation horizon within the column experiments. Acid-leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings, waste rock, or low-grade ores., Accelerated carbonation of ultramafic mine tailings has the potential to offset CO2 emissions produced by mining ores from Cu-Ni-platinum group element, podiform chromite, diamondiferous kimberlite, and historical chrysotile deposits. Implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore-processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures. Here, column experiments were designed to trial two geochemical treatments that address these criteria: direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation (10% CO2 in N2); and repeated heap leaching of ultramafic tailings with dilute sulphuric acid. In the first experiment, rapid carbonation of brucite [Mg(OH)2] is reported in the presence of 10% CO2 gas within tailings sampled from the Woodsreef chrysotile mine, New South Wales, Australia. Within four weeks, a doubling is observed of the amount of CO2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field. Reactive transport modelling (MIN3P) is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years. Finally, synchrotron X-ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals (Fe, Ni, Mn, Co, Cr) become highly concentrated within secondary Fe (hydr)oxide minerals at the pH neutralisation horizon within the column experiments. Acid-leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings, waste rock, or low-grade ores.

The Valmalenco area (central Alps, northern Italy) is well-known for the widespread mining and quarrying activities. Serpentinites are extracted and processed as valuable dimension stone in open-cast quarries, and a big underground mine provides talc as industrial mineral. The presence of long-fiber chrysotile veins, especially in the eastern part of the valley, gave rise in the past to widespread mining activity, particularly between the end of the XIX century and 1975, leaving huge amounts of mining waste and tailings. In recent times, part of the tailings have been stabilized and reclaimed, covered with soil and planted. Extensive sampling of mine tailings, soils and alluvial sediments was performed, to detect asbestos contamination (XRPD, SEM-EDS, TEM). Airborne asbestos was measured by environmental monitoring on polycarbonate filters (SEM and TEM), at the abandoned mines and at the closest centers. Huge amounts of chrysotile are still present in mine tailings (up to 20 wt.%), whereas soils and sediments were mostly below the 1000 ppm threshold; chrysotile is widespread almost in every part of the valley. Small amounts (< 400 ppm) of asbestiform tremolite were detected. Airborne asbestos was below the PEL of 2ff/l for living environments, with some peaks at mine dumps and close to active serpentine quarries. This preliminary study provides useful tips and effective technical measures for risk reduction in the extractive context.

Magnesium silicate hydrate (M–S–H) has been considered to play a significant role in different fields of engineering geology including radioactive waste disposal and geological storage of CO₂. However, M–S–H has been discussed only with synthetic samples in most previous studies. To confirm and characterize M–S–H precipitated in natural surface environments, and to assess the formation conditions and processes of the M–S–H, we investigated present-day precipitation of M–S–H at an ultramafic body in the Kamuikotan tectonic belt, Hokkaido, Japan. We collected seepage, surface water, and surface sediments on the ultramafic rock mass. Seepage and surface water showed alkaline pH and Mg²+–HCO₃- type water. Although bulk XRD analysis of the sediments did not clearly identify peaks of M–S–H due to its low crystallinity, microscopic observation showed that the sediments contained solid phases that are precipitated interstitially around the detrital serpentine particles. A TEM analysis identified the phases as M–S–H that may be mineralogically considered as a low-crystalline chrysotile with nano-tubular morphology. Thermodynamic calculations for the collected liquid samples suggest that mixed solution of seepage and surface water having high Si activity can induce the formation of M–S–H. The precipitation of M–S–H is likely to be a commonly occurring phenomenon in natural Mg–Si–H₂O systems where geochemical environments contain alkaline fluid that shows high Si activity and meets the thermodynamic conditions for M–S–H formation. In addition to the precipitation of M–S–H in Mg–Si–H₂O systems, we also observed that M–S–H is precipitated even under conditions including Ca and CO₂ species (i.e., Mg–Ca–Si–CO₂–H₂O systems), with a simultaneous precipitation of aragonite. This study supports an understanding of the precipitation of M–S–H by mineral–water interactions in natural surface/subsurface environments for various engineering geology fields.

The Valmalenco area (central Alps, northern Italy) is well-known for the widespread mining and quarrying activities. Serpentinites are extracted and processed as valuable dimension stone in open-cast quarries, and a big underground mine provides talc as industrial mineral. The presence of long-fiber chrysotile veins, especially in the eastern part of the valley, gave rise in the past to widespread mining activity, particularly between the end of the XIX century and 1975, leaving huge amounts of mining waste and tailings. In recent times, part of the tailings have been stabilized and reclaimed, covered with soil and planted. Extensive sampling of mine tailings, soils and alluvial sediments was performed, to detect asbestos contamination (XRPD, SEM-EDS, TEM). Airborne asbestos was measured by environmental monitoring on polycarbonate filters (SEM and TEM), at the abandoned mines and at the closest centers. Huge amounts of chrysotile are still present in mine tailings (up to 20 wt.%), whereas soils and sediments were mostly below the 1000 ppm threshold; chrysotile is widespread almost in every part of the valley. Small amounts (< 400 ppm) of asbestiform tremolite were detected. Airborne asbestos was below the PEL of 2ff/l for living environments, with some peaks at mine dumps and close to active serpentine quarries. This preliminary study provides useful tips and effective technical measures for risk reduction in the extractive context.

Serpentinite powdered samples from four different regions were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), SBET and porosity measurements, UV-Vis and Infrared Spectroscopy of the skeletal region and surface OH groups. SEM micrographs of the samples showed a prismatic morphology when the lizardite was the predominant phase, while if antigorite phase prevailed, the particles had a globular morphology. The few fibrous-shaped particles, only observed by SEM and weakly detected by XRD on MO-9C and MO13 samples, were characteristic of the chrysotile phase. All diffraction XRD patterns showed characteristic peaks of antigorite and lizardite serpentine phases, with crystallite sizes in the range 310–250 Å and with different degrees and types of carbonation processes, one derived from the transformation of the serpentine, generating dolomite, and another by direct precipitation of calcite. The SBET reached values between 38–24 m2∙g−1 for the samples less crystalline, in agreement with the XRD patterns, while those with a higher degree of crystallinity gave values close to 8–9 m2∙g−1. In the UV region all electronic spectra were dominated by the absorption edge due to O2− → Si4+ charge transfer transition, with Si4+ in tetrahedral coordination, corresponding to a band gap energy of ca 4.7 eV. In the visible region, 800–350 nm, the spectra of all samples, except Donai, presented at least two weak and broad absorptions centred in the range 650–800 and 550–360 nm, associated with the presence of Fe3+ ions from the oxidation of structural Fe2+ ions in the serpentinites ((MgxFe2+1−x)3Si2O5(OH)4). The relative intensity of the IR bands corresponding to the stretching modes of the OH’s groups indicated the prevalence of one of the two phases, antigorite or lizardite, in the serpentinites. We proposed that the different relative intensity of these bands could be considered as diagnostic to differentiate the predominance of these phases in serpenti, Universidad de Salamanca, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Chrysotile asbestos, the type produced in Zimbabwe, has the form of an extended sheet wrapped into a tubular structure and is almost chemically inert, being used in fire prevention and brake linings as it has a much wider range of favourable qualities than the far more dangerous amphibole, crocidolite and other brittle, splintery asbestos fibres. By 2016 there was no longer any significant production in Zimbabwe, the two largest mines at Shabanie and Gath's King section having effectively closed from 2009. The most significant deposits were associated with the Shabani sill and the Mashaba igneous complex. The fibres have a hydrothermal origin, arising from movement of aqueous solutions through dunite to form serpentinite with release and crystallisation of surplus Mg and SiO2 into chrysotile. The Shabanie deposits are a series of separate irregular, pod-like fibre orebodies within an area 4 km long and 1.5 km down-dip, varying from 500 000 tonnes to more than 15 000 000 t and separated by talc zones and dykes. The Mashaba or Mashava deposits are associated with a layered, predominantly ultramafic sill complex. Both Shabanie and Gath's started life as open pits, the incompetence of the orebodies and the need to avoid contamination leading to the development of caving methods of which block caving was the most cost-effective. The false-footwall mechanised method was developed at Gath's King section to overcome problems with unstable ground and to fit a configuration suitable for the steeply dipping natural footwall. Large re-investment of profits during the sanctions era resulted in massive mills being installed at Shabanie in the mid-1970s and at King section in the early 1980s; the fibres were separated from the ore by crushing, screening and air-lifting. Following firm correlation between asbestos and respiratory disease in the 1960s, further research led to a ban on smoking in the mines, so that lung cancer levels were no higher than elsewhere in Zimbabwe, and an, Chrysotile asbestos, the type produced in Zimbabwe, has the form of an extended sheet wrapped into a tubular structure and is almost chemically inert, being used in fire prevention and brake linings as it has a much wider range of favourable qualities than the far more dangerous amphibole, crocidolite and other brittle, splintery asbestos fibres. By 2016 there was no longer any significant production in Zimbabwe, the two largest mines at Shabanie and Gath's King section having effectively closed from 2009. The most significant deposits were associated with the Shabani sill and the Mashaba igneous complex. The fibres have a hydrothermal origin, arising from movement of aqueous solutions through dunite to form serpentinite with release and crystallisation of surplus Mg and SiO2 into chrysotile. The Shabanie deposits are a series of separate irregular, pod-like fibre orebodies within an area 4 km long and 1.5 km down-dip, varying from 500 000 tonnes to more than 15 000 000 t and separated by talc zones and dykes. The Mashaba or Mashava deposits are associated with a layered, predominantly ultramafic sill complex. Both Shabanie and Gath's started life as open pits, the incompetence of the orebodies and the need to avoid contamination leading to the development of caving methods of which block caving was the most cost-effective. The false-footwall mechanised method was developed at Gath's King section to overcome problems with unstable ground and to fit a configuration suitable for the steeply dipping natural footwall. Large re-investment of profits during the sanctions era resulted in massive mills being installed at Shabanie in the mid-1970s and at King section in the early 1980s; the fibres were separated from the ore by crushing, screening and air-lifting. Following firm correlation between asbestos and respiratory disease in the 1960s, further research led to a ban on smoking in the mines, so that lung cancer levels were no higher than elsewhere in Zimbabwe, and an

Introduction A retrospective cohort study of employees of one of the world's largest chrysotile asbestos mine and mills (JSC Uralasbest, Asbest, Russia) is presently being conducted. The primary aim of the study is to more precisely characterise and quantify the exposure-response relationship for total and sitespecific cancer risks associated with chrysotile exposure. Methods The study includes workers employed for at least one year during 1975-2010 in the mine, enrichment factories, transportation, laboratory, and the explosives unit. Ascertainment of cohort members through extraction of occupational histories from the enterprises' archives started in 2012. Results At present, the cohort comprises more than 35 000 workers. A detailed occupational history was collected for each cohort member. Temporal trends in exposure levels were analysed using a database containing 89 290 monthly-averaged gravimetric dust concentrations from stationary sampling points in the enrichment factories (1951-2001) and 1457 in the mine (1964-2001). Parallel gravimetric and fibre (PCOM) concentrations were used to estimate dust to fibre conversion factors. Currently a job-exposure matrix is being developed to translate individuals' job histories into exposure histories for both dust and fibre concentrations. Sverdlovsk region mortality data of cohort members have been ascertained by linkage with medical death certificates recorded at the Sverdlovsk Regional Civil Acts Registration Office. In addition, a comparison of mortality rates in Asbest city and in Sverdlovsk region (1997- 2010) was performed. Further efforts are ongoing to ascertain vital status and migration of cohort members from Sverdlovsk region. A parallel cross-sectional survey aimed at estimating tobacco smoking in current workers and veterans (more than 7000 participants) was conducted. Conclusion The study will continue through 2019. Given the large size of the cohort, the large proportion of female workers and the detaile

Asbestos fibers are highly toxic (Group 1 carcinogen) due to their high aspect ratio, durability, and the presence of iron. In nature, plants, fungi, and microorganisms release exudates, which can alter the physical and chemical properties of soil minerals including asbestos minerals. We examined whether exudates from bacteria and fungi at environmentally relevant concentrations can alter chrysotile, the most widely used asbestos mineral, and lower its toxicity. We monitored the release of iron from chrysotile in the presence of organic acid ligands and iron-specific siderophores derived from bacteria and fungi and measured any change in fiber toxicity toward peritoneal macrophages harvested from mice. Both fungal and bacterial siderophores increased the removal of iron from asbestos fibers. In contrast, organic acid ligands at environmentally relevant concentrations neither released iron from fibers nor helped in siderophore-mediated iron removal. Removal of plant-available or exchangeable iron did not diminish iron dissolution by both types of siderophores, which indicates that siderophores can effectively remove structural iron from chrysotile fibers. Removal of iron by siderophore lowered the fiber toxicity; fungal siderophore appears to be more effective than bacterial siderophore in lowering the toxicity. These results indicate that prolonged exposure to siderophores, not organic acids, in the soil environment decreases asbestos fiber toxicity and possibly lowers the health risks. Thus, bioremediation should be explored as a viable strategy to manage asbestos-contaminated sites such as Brownfield sites, which are currently left untreated despite dangers to surrounding communities.

Objectives: Mining and processing of chrysotile, an established carcinogen, has been undertaken in Asbest, Russian Federation since the late 1800s. Dust concentrations were routinely recorded at the open-pit mine and its asbestos-enrichment factories. We examined the temporal trends in these dust concentrations from 1951 to 2001.Methods: Analyses included 89290 monthly averaged gravimetric dust concentrations in six factories (1951-2001) and 1457 monthly averaged concentrations in the mine (1964-2001). Annual percent changes (APC) in geometric mean dust concentrations were estimated for each factory and the mine separately from linear mixed models of the logarithmic-transformed monthly averaged concentrations.Results: Dust concentrations declined significantly in the mine [APC: -1.6%; 95% confidence interval (CI): -3.0 to -0.2] and Factories 1-5 but not 6. Overall factory APCs ranged from -30.4% (95% CI: -51.9 to -8.9; Factory 1: 1951-1955) to -0.6% (95% CI: -1.5 to 0.2; Factory 6: 1969-2001). Factory trends varied across decades, with the steepest declines observed before 1960 [APCs: -21.5% (Factory 2) and -17.4% (Factory 3)], more moderate declines in the 1960s and 1970s [APCs from -10% in Factory 2 (1960s) to -0.3% (not statistically significant) in Factory 4 (1970s)], and little change thereafter. Mine dust concentrations increased in the 1960s (APC: +9.7%; 95% CI: 3.6 to 15.9), decreased in the 1990s (APC: -5.8%; 95% CI: -8.1 to -3.5) and were stable in between.Conclusions: In this analysis of >90000 dust concentrations, factory dust concentrations declined between 1951 and 1979 and then stabilized. In the mine, dust levels increased in the 1960s, declined in the 1990s and were unchanged in the interim.

INTRODUCTION: Historic dust concentrations are available in a large-scale cohort study of workers in a chrysotile mine and processing factories in Asbest, Russian Federation. Parallel dust (gravimetric) and fibre (phase-contrast optical microscopy) concentrations collected in 1995, 2007 and 2013/14 were used to determine if dust to fibre conversion factors can be estimated.MATERIALS/SUBJECTS AND METHODS: Daily medians of multiple parallel dust and fibre concentrations by sampling points were used to derive fibre to dust ratios. Applying linear mixed models, we estimated best linear unbiased predictions for the fibre to dust ratios.RESULTS AND DISCUSSION: A total of 620 daily median fibre to dust ratios were derived. In the factories, modelled ratios varied by unit, increasing along the stages of asbestos enrichment as expected. In the mine, ratios were higher in winter compared to summer. Overall, the ratios showed a strong negative dependency on dust concentration.CONCLUSIONS: Our study shows that dust to fibre conversion is possible by unit but extrapolations are needed. The patterns for exposure by dust and fibre will be similar but estimated fibre levels will show less contrast due to the conversion factor being smaller at higher dust concentrations.

This work reports the results of the structural study of three representative chrysotile samples of different provenance (Canadian UICC, and Italian Balangero and Valmalenco). Chemical composition was determined using EMPA and TG data. An innovative wet cryo-milling procedure was used to powder the flexible and durable chrysotile fibres. X-ray powder diffraction patterns were collected using both conventional and nonconventional sources. Collected data were used for Rietveld structural refinements and results were compared with available literature data. The three samples display similar structure models, although small differences were detected in the position of the oxygen atoms. Both the structural refinements and spectroscopic investigations confirms that Fe2+ and Fe3+ atoms in chrysotile are located in the octahedral cavities only, substituting for Mg2+. Regarding the atom coordinates, UICC chrysotile is the closest to the model reported by Falini et al. (2004). About the lattice parameters, the Valmalenco chrysotile is the closest, if compared with the Balangero and UICC, to both the model proposed by Whittaker (1956a,b) and Falini et al. (2004). This work is intended as a basis for subsequent studies aimed at understanding the toxicity of these mineral fibres.

This work reports the results of the structural study of three representative chrysotile samples of different provenance (Canadian UICC, and Italian Balangero and Valmalenco). Chemical composition was determined using EMPA and TG data. An innovative wet cryo-milling procedure was used to powder the flexible and durable chrysotile fibres. X-ray powder diffraction patterns were collected using both conventional and nonconventional sources. Collected data were used for Rietveld structural refinements and results were compared with available literature data. The three samples display similar structure models, although small differences were detected in the position of the oxygen atoms. Both the structural refinements and spectroscopic investigations confirms that Fe2+ and Fe3+ atoms in chrysotile are located in the octahedral cavities only, substituting for Mg2+. Regarding the atom coordinates, UICC chrysotile is the closest to the model reported by Falini et al. (2004). About the lattice parameters, the Valmalenco chrysotile is the closest, if compared with the Balangero and UICC, to both the model proposed by Whittaker (1956a,b) and Falini et al. (2004). This work is intended as a basis for subsequent studies aimed at understanding the toxicity of these mineral fibres.

Mineral fibres are ubiquitous on Earth. Because many of them possess outstanding technological properties, they have been used since ancient times for a huge number of applications. They are considered now one of the most interesting and complex examples of inorganic to organic sphere interaction with direct consequences for human health. The most important mineral fibres are serpentine asbestos (chrysotile), amphibole asbestos species and the zeolite erionite. If inhaled, because of their peculiar fibrous-asbestiform crystal habit and chemical-physical surface reactivity, these mineral fibres may induce, after a long latency period, fatal lung diseases. All amphibole asbestos minerals are banned worldwide whereas chrysotile is banned only in the countries strictly following the indication of the International Agency for Research on Cancer (IARC) which includes chrysotile in Group 1 "substance carcinogenic to humans". No ban has been proposed for the zeolite erionite so far. Explaining human toxicity of mineral fibres is not straightforward at all. The difficulties stem from the fact that mineral fibres possess a variety of chemical compositions, atomic structural arrangements, morphologies that affect biogeochemical reactions in the body. Due to the interplay of all these factors, the mechanisms by which mineral fibres induces cyto- and geno-toxic damage remain unclear. Our research group is actually involved in the study of the bio-interaction and toxicity of the mineral fibres from the well pondered assemblage of chemical-physical, mineralogical-structural, and biological information. In this work, we present the results of the mineralogical and chemical physical characterization of mineral fibres belonging to the major classes of mineral fibres of economic and social importance: three chrysotile species including the UICC standard, Balangero and Valmalenco (Italy), crocidolite UICC standard, amosite from Penge (South Africa), anthophyllite UICC standard, tremoli

PURPOSE: Existing estimated lung cancer risks per unit of asbestos exposure are mainly based on, and applicable to, high exposure levels. To assess the risk at low cumulative asbestos exposure, we provide new evidence by fitting flexible meta-regression models, a notably new and more robust method. METHODS: Studies were selected if lung cancer risk per cumulative asbestos exposure in at least two exposure categories was reported. From these studies (n = 19), we extracted 104 risk estimates over a cumulative exposure range of 0.11-4,710 f-y/ml. We fitted linear and natural spline meta-regression models to these risk estimates. A natural spline allows risks to vary nonlinearly with exposure, such that estimates at low exposure are less affected by estimates in the upper exposure categories. Associated relative risks (RRs) were calculated for several low cumulative asbestos exposures. RESULTS: A natural spline model fitted our data best. With this model, the relative lung cancer risk for cumulative exposure levels of 4 and 40 f-y/ml was estimated between 1.013 and 1.027, and 1.13 and 1.30, respectively. After stratification by fiber type, a non-significant three- to fourfold difference in RRs between chrysotile and amphibole fibers was found for exposures below 40 f-y/ml. Fiber-type-specific risk estimates were strongly influenced by a few studies. CONCLUSIONS: The natural spline regression model indicates that at lower asbestos exposure levels, the increase in RR of lung cancer due to asbestos exposure may be larger than expected from previous meta-analyses. Observed potency differences between different fiber types are lower than the generally held consensus. Low-exposed industrial or population-based cohorts with quantitative estimates of asbestos exposure a required to substantiate the risk estimates at low exposure levels from our new, flexible meta-regression.

The Valmalenco serpentinite (central Alps, northern Italy) is marketed worldwide as dimension and decorative stone. However, the same area was once subject to chrysotile asbestos mining, from the XIX century till 1975. Asbestos is a well-known carcinogen, and there is the possibility of releasing fibres during quarrying, subsequently exposing workers. From 2004 till 2011, extensive sampling and monitoring of quarry fronts, asbestos veins, commercial stones and airborne asbestos was carried out. Massive rock and vein samples were analyzed by a combined use of optical microscopy, X-ray powder diffraction (XRPD) and quantitative electron microscopy (SEM). Asbestos is concentrated almost exclusively in discrete horizons, that coincide with the main discontinuities of the rock mass. Commercial stones without fractures and veins are practically asbestos free, whereas there is a slight contamination (sometimes exceeding the 1,000 ppm threshold) close to hydrothermal salvages. Quarry floors were always quite contaminated by chrysotile “beards” detached from the surface of the blocks. The airborne asbestos concentrations (PCM and SEM) were distributed over a wide range, mostly below the occupational exposure limit of 0.1 fml-1. Concentrations at quarry property border or at the closest villages were always below the environmental exposure limit of 0.002 fml-1. The extreme thinness of chrysotile fibrils produced during quarrying activities, and the abundance of pseudo-fibrous antigorite cleavage fragments proved the SEM-EDS analytical procedure to be the most suitable. It is of crucial importance to avoid the interception of veins during quarrying and to remove all visible asbestos from the extracted blocks, before any further processing

The Valmalenco serpentinite (central Alps, northern Italy) is marketed worldwide as dimension and decorative stone. However, the same area was once subject to chrysotile asbestos mining, from the XIX century till 1975. Asbestos is a well-known carcinogen, and there is the possibility of releasing fibres during quarrying, subsequently exposing workers. From 2004 till 2011, extensive sampling and monitoring of quarry fronts, asbestos veins, commercial stones and airborne asbestos was carried out. Massive rock and vein samples were analyzed by a combined use of optical microscopy, X-ray powder diffraction (XRPD) and quantitative electron microscopy (SEM). Asbestos is concentrated almost exclusively in discrete horizons, that coincide with the main discontinuities of the rock mass. Commercial stones without fractures and veins are practically asbestos free, whereas there is a slight contamination (sometimes exceeding the 1,000 ppm threshold) close to hydrothermal salvages. Quarry floors were always quite contaminated by chrysotile “beards” detached from the surface of the blocks. The airborne asbestos concentrations (PCM and SEM) were distributed over a wide range, mostly below the occupational exposure limit of 0.1 fml-1. Concentrations at quarry property border or at the closest villages were always below the environmental exposure limit of 0.002 fml-1. The extreme thinness of chrysotile fibrils produced during quarrying activities, and the abundance of pseudo-fibrous antigorite cleavage fragments proved the SEM-EDS analytical procedure to be the most suitable. It is of crucial importance to avoid the interception of veins during quarrying and to remove all visible asbestos from the extracted blocks, before any further processing

Outcrops of serpentinites are usually strongly fractured and cataclastic, and the rock can only be used as ballast. However, in rare cases, like in Valmalenco (Central Alps, Northern Italy), fractures are regular and well spaced, and the rock mass has good geotechnical quality, ideal conditions for the extraction of dimension stone blocks. The Valmalenco Serpentinite is marketed worldwide as dimension and decorative stone, with remarkable mechanical properties and pleasing colours and textures. However, the same area was once subject to chrysotile asbestos mining, in the form of discrete veins along the main discontinuities of the rock mass. For this reason, airborne asbestos contamination can occur during the extraction and processing cycle of the rocks, therefore it is essential to locate and quantify asbestos in the rock mass, to reduce as much as possible the exposure risk. The first step was a detailed geostructural survey of each quarry, in order to characterize the main discontinuities (orientation, spacing, linear persistence, opening, filling), with special attention to the identification of fibrous minerals. The surveys was followed by extensive sampling of massive rocks, mineralized veins and fillings of fractures, and the cutting sludge derived from diamond wire cutting. Preliminary qualitative XRPD was performed on all samples, while quantitative analysis was carried out on the most representative samples of the main rock mass discontinuities. On the other hand, XRPD is not effective in the identification of asbestos percentages of less than 2% by weight, and the accurate distinction among the various serpentine polymorphs (antigorite, lizardite, chrysotile) is very difficult (if not impossible) when they are simultaneously present, due to their very similar basic structure and the strong structural disorder. The same samples were then analyzed by SEM-EDS (fiber counting after filtration on a polycarbonate filter), for a better distinction between fibro

In 2011, we reported on the sensitivity of lung cancer potency estimates for asbestos to the quality of the exposure assessment component of underlying evidence. Both this meta-analysis and a separate reassessment of standards published by the Health Council of the Netherlands (Gezondheidsraad) have been commented on by Berman and Case. A criticism is that we used a truncated data set. We incrementally excluded poorer-quality studies to evaluate trends in meta-analyzed lung cancer potency estimates (meta-K (L) values). This was one of three analysis approaches we presented. The other two used the full set of studies: a meta-analysis stratified by covariates and dichotomized by poorer and better exposure assessment aspects; and a meta-regression modeling both asbestos fiber type and these covariates. They also state that our results are not robust to removal of one study. We disagree with this claim and present additional sensitivity analyses underpinning our earlier conclusion that inclusion of studies with higher-quality asbestos-exposure assessment yield higher meta-estimates of the lung cancer risk per unit of exposure. We reiterate that potency differences for predominantly chrysotile- versus amphibole-asbestos-exposed cohorts are difficult to ascertain when meta-analyses are restricted to studies with fewer exposure assessment limitations. We strongly argue that the existence of any uncertainty related to potency issues should not hamper the development of appropriate evidence-based guidelines and stringent policies in order to protect the public from hazardous environmental and occupational exposures.

A description is presented of the Pietersburg and Pilgrim's Rest goldfields and other early discoveries along the Transvaal Drakensberg escarpment in South Africa. The history of gold discoveries in the Archaean volcano-sedimentary successions of the Barberton greenstone belt is discussed including photographs of early mining activities. The total production of gold in the Barberton goldfield since its inception in 1884 is estimated to have been 360 t with most in recent years coming from five mines: Sheba, New Consort, Fairview, Agnes and Lily. Other mineral discoveries in the Barberton greenstone belt are described, among them significant deposits of chrysotile asbestos, iron ore, magnesite, talc and barite together with occurrences of semi-precious commodities (verdite, buddstone, copper-nickel, antimony, mercury, tin-tungsten and zinc)., A description is presented of the Pietersburg and Pilgrim's Rest goldfields and other early discoveries along the Transvaal Drakensberg escarpment in South Africa. The history of gold discoveries in the Archaean volcano-sedimentary successions of the Barberton greenstone belt is discussed including photographs of early mining activities. The total production of gold in the Barberton goldfield since its inception in 1884 is estimated to have been 360 t with most in recent years coming from five mines: Sheba, New Consort, Fairview, Agnes and Lily. Other mineral discoveries in the Barberton greenstone belt are described, among them significant deposits of chrysotile asbestos, iron ore, magnesite, talc and barite together with occurrences of semi-precious commodities (verdite, buddstone, copper-nickel, antimony, mercury, tin-tungsten and zinc).

The paper addresses the issue of health risk associated with the presence of chrysotile in the soil type ranker formed on massive serpentines occurring in the area of Bubanj Potok, a settlement located in the southern Belgrade environs, Serbia. Characterization of the ranker soil was conducted by scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy and transmission Fe-57 Mossbauer spectroscopy. Scanning electron microscopy figures showed regular shaped smectite (montmorillonite) particles, aggregates of chlorite, and elongated sheets of serpentines minerals antigorite. X-ray diffraction analysis confirmed the presence of detrital mineral quartz polymorph as well as minor amounts of other mineral species. Micro-Raman spectroscopy identified the presence of dominant minerals, such as montmorillonite, kaolinite, muscovite, gypsum, calcite, albite, amphiboles (hornblende/kaersutite) and orthoclase. Important polymorph silica modifications of quartz, olivine (forsterite), pyroxene (enstatite/ferrosilite, diopside/hedenbergite), and serpentine (antigorite/lizardite/chrysotile) were identified.

The paper addresses the issue of health risk associated with the presence of chrysotile in the soil type ranker formed on massive serpentines occurring in the area of Bubanj Potok, a settlement located in the southern Belgrade environs, Serbia. Characterization of the ranker soil was conducted by scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy and transmission Fe-57 Mossbauer spectroscopy. Scanning electron microscopy figures showed regular shaped smectite (montmorillonite) particles, aggregates of chlorite, and elongated sheets of serpentines minerals antigorite. X-ray diffraction analysis confirmed the presence of detrital mineral quartz polymorph as well as minor amounts of other mineral species. Micro-Raman spectroscopy identified the presence of dominant minerals, such as montmorillonite, kaolinite, muscovite, gypsum, calcite, albite, amphiboles (hornblende/kaersutite) and orthoclase. Important polymorph silica modifications of quartz, olivine (forsterite), pyroxene (enstatite/ferrosilite, diopside/hedenbergite), and serpentine (antigorite/lizardite/chrysotile) were identified.

The paper addresses the issue of health risk associated with the presence of chrysotile in the soil type ranker formed on massive serpentines occurring in the area of Bubanj Potok, a settlement located in the southern Belgrade environs, Serbia. Characterization of the ranker soil was conducted by scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy and transmission 57Fe Mössbauer spectroscopy. Scanning electron microscopy figures showed regular shaped smectite (montmorillonite) particles, aggregates of chlorite, and elongated sheets of serpentines minerals antigorite. X-ray diffraction analysis confirmed the presence of detrital mineral quartz polymorph as well as minor amounts of other mineral species. Micro-Raman spectroscopy identified the presence of dominant minerals, such as montmorillonite, kaolinite, muscovite, gypsum, calcite, albite, amphiboles (hornblende/kaersutite) and orthoclase. Important polymorph silica modifications of quartz, olivine (forsterite), pyroxene (enstatite/ferrosilite, diopside/hedenbergite), and serpentine (antigorite/lizardite/chrysotile) were identified., Rad se bavi pitanjem zdravstvenog rizika povezanog sa prisustvom hrizotila u rankeru (tip zemljišta) formiranom na masivnom serpentinitu u oblasti Bubanj Potoka, naselju koje se nalazi u južnoj okolini Beograda. Karakterizacija rankera je izvršena skenirajućom elektronskom mikroskopijom, rendgenskom difrakcijom praha, mikro-Raman spektroskopijom i transmisionom 57Fe Mesbauer spektroskopijom. Slike dobijene skenirajućim elektronskim mikroskopom pokazuju čestice smektita regularnog oblika montmorionita, agregata hlorita i izdužene listove serpentinskog minerala antigorita. Rendgenska difrakciona analiza potvrdila je prisustvo detrital minerala kvarcnog polimorfa kao i manje količine drugih mineralnih vrsta. Mikro-Raman spektroskopija identifikovala je prisustvo dominantnih minerala, kao što su montmorionit i kaolinit, muskovit, gips, kalcit, albit, amfibol (kaersutit/hornblenda) i ortoklas. Važni polimorfi silika modifikacije kvarca, olivina (forsterit), piroksena (enstatit, ferosilit, hedenbergit, diopsid), i serpentina (antigorit, lizardit, hrizotil) su bili identifikovani.

Background: Asbestos is a well-recognized cause of lung cancer, but there is considerable between-study heterogeneity in the slope of the exposure-response relationship.Objective: We considered the role of quality of the exposure assessment to potentially explain heterogeneity in exposure-response slope estimates.Data sources: We searched PubMed MEDLINE (1950-2009) for studies with quantitative estimates of cumulative asbestos exposure and lung cancer mortality and identified 19 original epidemiological studies. One was a population-based case-control study, and the others were industry-based cohort studies.Data extraction: Cumulative exposure categories and corresponding risks were abstracted. Exposure-response slopes [KL (lung cancer potency factor of asbestos)] were calculated using linear relative risk regression models.Data synthesis: We assessed the quality of five exposure assessment aspects of each study and conducted random effects univariate and multivariate meta-regressions. Heterogeneity in exposure-response relationships was greater than expected by chance (I2 = 64%). Stratification by exposure assessment characteristics revealed that studies with well-documented exposure assessment, larger contrast in exposure, greater coverage of the exposure history by exposure measurement data, and more complete job histories had higher meta-KL values than did studies without these characteristics. The latter two covariates were most strongly associated with the KL value. Meta-KL values increased when we incrementally restricted analyses to higher-quality studies.Conclusions: This meta-analysis indicates that studies with higher-quality asbestos exposure assessment yield higher meta-estimates of the lung cancer risk per unit of exposure. Potency differences for predominantly chrysotile versus amphibole asbestos-exposed cohorts become difficult to ascertain when meta-analyses are restricted to studies with fewer exposure assessment limitations.

The project and the works described in this article mainly deal with the removal of the current asbestos-cement covering of the roof of the Central Market in Alicante and its replacement with zinc diamond-shaped scales, similar to the originals which were implemented in 1921 when the building was put into service. These upgrades were necessary to avoid the causes (and consequences) of rainwater infiltration, as described in an earlier report in 2006, also drafted by the author of this article. The article illustrates the difficulties involving the practical application of Spanish Code RD 396/2006 (minimum safety and health requirements for work with risk of exposure to asbestos) in a complex case such as this, especially with regard to aspects such as economic (increasing costs), technical (increased difficulty of implementation), and the total duration of the work (total increase in duration due to interference with other trades).

The National Interest Site for remediation of Balangero and Corio produced chrysotile from the 1918 and in the 1970s became the largest European asbestos mine, causing a considerable contamination of the area.The mine was closed in the 1990 because the D.L. 257/92 banned the extraction, import, export, marketing and production of asbestos.The objective of the competition was not only to reclaim a contaminated area, but also to enhance culture and landscape, to preserve the historical memory and to promote initiatives involving the local population to restore the economic and social strength of the region.The project proposes the conversion of the industrial buildings into spaces for documenting the mine history, places for production and promotion of arts and a range of accommodation aimed at developing different forms of tourism.

The project and the works described in this article mainly deal with the removal of the current asbestos-cement covering of the roof of the Central Market in Alicante and its replacement with zinc diamond-shaped scales, similar to the originals which were implemented in 1921 when the building was put into service. These upgrades were necessary to avoid the causes (and consequences) of rainwater infiltration, as described in an earlier report in 2006, also drafted by the author of this article. The article illustrates the difficulties involving the practical application of Spanish Code RD 396/2006 (minimum safety and health requirements for work with risk of exposure to asbestos) in a complex case such as this, especially with regard to aspects such as economic (increasing costs), technical (increased difficulty of implementation), and the total duration of the work (total increase in duration due to interference with other trades).

Chrysotile occurs as a major gangue mineral in many ores, such as the low-grade Ni ores of Mount Keith in Western Australia. The effect of its distinct morphology and surface charge on its rheological behaviour in pure suspensions was investigated. The results of the study show that the chrysotile surface is positively charged over a broad pH range (pH 2-10). The disparity between the point of zero charge (pH 8.23) and the yield stress peak range (pH 5-9) are consistent with the anisotropic nature of chrysotile. Its long thin fibres are easily entangled, forming suspensions with higher plastic viscosities and Bingham yield stresses than those made from non-fibrous minerals such as quartz. The shape of the chrysotile particles appears to be more significant than the surface charge in the rheology., Chrysotile occurs as a major gangue mineral in many ores, such as the low-grade Ni ores of Mount Keith in Western Australia. The effect of its distinct morphology and surface charge on its rheological behaviour in pure suspensions was investigated. The results of the study show that the chrysotile surface is positively charged over a broad pH range (pH 2-10). The disparity between the point of zero charge (pH 8.23) and the yield stress peak range (pH 5-9) are consistent with the anisotropic nature of chrysotile. Its long thin fibres are easily entangled, forming suspensions with higher plastic viscosities and Bingham yield stresses than those made from non-fibrous minerals such as quartz. The shape of the chrysotile particles appears to be more significant than the surface charge in the rheology.

The Dzhetygara asbestos deposit in Kazakhstan is characterised by significant variations in the total content of fibre fractions of +0.5 mm and asbestos fractions of +4.8 mm and -4.8+1.35 mm. The deposit has been exploited for a number of years and the reserves are being depleted and the ores have a lower content of valuable components. Processing of ores with variable quality results in problems in beneficiating the ore, deterioration of the quality of the final product, reduced output and higher asbestos losses to the tailings. A new preparation system was introduced in 2006 to manage ore flow from different blocks with different qualities in relation to type of ore, asbestos content and difficulty of enrichment. Blending of ores is carried out in storehouses which have a special pit consisting of a trench 25 m long and 3.5 m deep. The storehouse is divided into two areas, one for ore stacking and blending and one for ore shipment. Delivery of the ore to the concentration plant is carried out from different parts of the storehouse in accordance with a formula which is used to average the ore quality. Production of commercial chrysotile-asbestos grades has increased by 17 682 t, the processing of easy to enrich ores has decreased by 366 000 t, the quantity of difficult to enrich ores from the southern and central parts of the deposit has increased by 90 000 t and operating costs for producing commercial asbestos grades has decreased by 2.8%., The Dzhetygara asbestos deposit in Kazakhstan is characterised by significant variations in the total content of fibre fractions of +0.5 mm and asbestos fractions of +4.8 mm and -4.8+1.35 mm. The deposit has been exploited for a number of years and the reserves are being depleted and the ores have a lower content of valuable components. Processing of ores with variable quality results in problems in beneficiating the ore, deterioration of the quality of the final product, reduced output and higher asbestos losses to the tailings. A new preparation system was introduced in 2006 to manage ore flow from different blocks with different qualities in relation to type of ore, asbestos content and difficulty of enrichment. Blending of ores is carried out in storehouses which have a special pit consisting of a trench 25 m long and 3.5 m deep. The storehouse is divided into two areas, one for ore stacking and blending and one for ore shipment. Delivery of the ore to the concentration plant is carried out from different parts of the storehouse in accordance with a formula which is used to average the ore quality. Production of commercial chrysotile-asbestos grades has increased by 17 682 t, the processing of easy to enrich ores has decreased by 366 000 t, the quantity of difficult to enrich ores from the southern and central parts of the deposit has increased by 90 000 t and operating costs for producing commercial asbestos grades has decreased by 2.8%.

Rheological tests were carried out on samples of flotation pulp obtained in the processing of a finely ground Ni sulphide ore containing 0.5% Ni and with pentlandite, millerite and violarite as the main Ni-bearing minerals. The serpentinised ultramafic gangue mainly contained lizardite, antigorite and the needle-like chrysotile. Tests were also carried on aqueous chrysotile suspensions, and the results compared with literature data obtained in model tests which indicate that the shape of the particles strongly affects the rheology of mineral suspensions. Comparison of the rheological properties of the chrysotile suspensions with model systems using nylon threads of different length/diameter (L/D) ratios indicated that the L/D ratio for the chrysotile particles was larger than 156. The very high yield stress values may also result to some extent from coulombic particle-particle interactions. The yield stress values in the ore samples were much lower, but still high compared with systems containing particles of well-defined shape, indicating that the high pulp viscosities were due to high contents of chrysotile particles. The rheological curves for the finely ground ore indicated that the maximum packing fraction for the fine fraction was close to 8 vol%, and explains why this fraction could not be floated at pulp densities higher than 20 wt%., Rheological tests were carried out on samples of flotation pulp obtained in the processing of a finely ground Ni sulphide ore containing 0.5% Ni and with pentlandite, millerite and violarite as the main Ni-bearing minerals. The serpentinised ultramafic gangue mainly contained lizardite, antigorite and the needle-like chrysotile. Tests were also carried on aqueous chrysotile suspensions, and the results compared with literature data obtained in model tests which indicate that the shape of the particles strongly affects the rheology of mineral suspensions. Comparison of the rheological properties of the chrysotile suspensions with model systems using nylon threads of different length/diameter (L/D) ratios indicated that the L/D ratio for the chrysotile particles was larger than 156. The very high yield stress values may also result to some extent from coulombic particle-particle interactions. The yield stress values in the ore samples were much lower, but still high compared with systems containing particles of well-defined shape, indicating that the high pulp viscosities were due to high contents of chrysotile particles. The rheological curves for the finely ground ore indicated that the maximum packing fraction for the fine fraction was close to 8 vol%, and explains why this fraction could not be floated at pulp densities higher than 20 wt%.

Anisotropic minerals are important constituents of many ores, including valuable minerals such as molybdenite in Cu-Mo ores and gangue minerals such as talc in Pt-containing sulphide ores from South Africa, graphite in Cu-Ni sulphide ores from Canada, chrysotile in Ni sulphide ores in Australia and clay minerals in all types of ore. The structures of clays, molybdenite, graphite and talc are discussed, a commonality being that they all have a laminar crystal structure, and their flotation and rheological properties are reviewed. While there is good correlation between the rheological properties and the pH of the iso-electric point for suspensions of isotropic minerals, this is not the case for anisotropic minerals due to deficiencies in electrokinetic techniques for measuring the electrokinetic potential of the plate- or needle-like anisotropic particles and the existence of very different electrical charges on the various sides of the mineral particles., Anisotropic minerals are important constituents of many ores, including valuable minerals such as molybdenite in Cu-Mo ores and gangue minerals such as talc in Pt-containing sulphide ores from South Africa, graphite in Cu-Ni sulphide ores from Canada, chrysotile in Ni sulphide ores in Australia and clay minerals in all types of ore. The structures of clays, molybdenite, graphite and talc are discussed, a commonality being that they all have a laminar crystal structure, and their flotation and rheological properties are reviewed. While there is good correlation between the rheological properties and the pH of the iso-electric point for suspensions of isotropic minerals, this is not the case for anisotropic minerals due to deficiencies in electrokinetic techniques for measuring the electrokinetic potential of the plate- or needle-like anisotropic particles and the existence of very different electrical charges on the various sides of the mineral particles.

Tests were carried out on a Ni sulphide ore containing 0.5% Ni with pentlandite, millerite and violarite as the main minerals. The serpentinised ultramafic gangue mainly contained lizardite, together with antigorite and chrysotile. Samples were ground to 80% smaller than 125 micrometres and subjected to flotation using an isobutyl xanthate collector. After a 10 minute conditioning period, 200-500 g/t diesel oil was added. The power draw measurements were made using a low-friction turntable which rotated when the impeller was turned on. The utility of the power draw measurements was also studied in the agglomeration of fine coal. Power draw measurements during the conditioning stage confirmed a good correlation with the pulp rheology determined using conventional techniques. The method can be used to follow the agglomeration of fine particles, as in the oil agglomeration of fine bituminous coal, but depends on the ratio of the number of agglomerating particles to the total number of particles in the system and becomes very imprecise when the ratio is not large. Additions of 2-5% of the finely ground Ni sulphide ore to the agglomerating suspensions of fine bituminous coal completely masked the effect of agglomeration on the measured power draw, indicating that the shape of the gangue particles played an important role in the system, Tests were carried out on a Ni sulphide ore containing 0.5% Ni with pentlandite, millerite and violarite as the main minerals. The serpentinised ultramafic gangue mainly contained lizardite, together with antigorite and chrysotile. Samples were ground to 80% smaller than 125 micrometres and subjected to flotation using an isobutyl xanthate collector. After a 10 minute conditioning period, 200-500 g/t diesel oil was added. The power draw measurements were made using a low-friction turntable which rotated when the impeller was turned on. The utility of the power draw measurements was also studied in the agglomeration of fine coal. Power draw measurements during the conditioning stage confirmed a good correlation with the pulp rheology determined using conventional techniques. The method can be used to follow the agglomeration of fine particles, as in the oil agglomeration of fine bituminous coal, but depends on the ratio of the number of agglomerating particles to the total number of particles in the system and becomes very imprecise when the ratio is not large. Additions of 2-5% of the finely ground Ni sulphide ore to the agglomerating suspensions of fine bituminous coal completely masked the effect of agglomeration on the measured power draw, indicating that the shape of the gangue particles played an important role in the system

The correlation was investigated between the rheological properties of the flotation pulp and the flotation response of a very finely ground ore containing 0.5% Ni and pentlandite, millerite and violarite as the main minerals. The gangue contained lizardite, antigorite and chrysotile. The chrysotile had a flexible fibrous structure and was considered to be a main reason for the difficulty in processing the ore. The results of rheological and batch flotation tests confirmed that the flotation performance was strongly dependent on pulp density. Grade/recovery curves showed that concentrate yield increased and concentrate grade declined significantly as the pulp density increased from 5 to 20 wt%. Pulp viscosities increased when the solids content approached 20 wt%, indicating that the maximum packing fraction for the ore was about 8 vol%. The concentrate grades increased at Casson yield stresses above 1.5-2 Pa and a boiling effect was observed which was probably due to the high viscosity., The correlation was investigated between the rheological properties of the flotation pulp and the flotation response of a very finely ground ore containing 0.5% Ni and pentlandite, millerite and violarite as the main minerals. The gangue contained lizardite, antigorite and chrysotile. The chrysotile had a flexible fibrous structure and was considered to be a main reason for the difficulty in processing the ore. The results of rheological and batch flotation tests confirmed that the flotation performance was strongly dependent on pulp density. Grade/recovery curves showed that concentrate yield increased and concentrate grade declined significantly as the pulp density increased from 5 to 20 wt%. Pulp viscosities increased when the solids content approached 20 wt%, indicating that the maximum packing fraction for the ore was about 8 vol%. The concentrate grades increased at Casson yield stresses above 1.5-2 Pa and a boiling effect was observed which was probably due to the high viscosity.

The effect is discussed of the mineralogy of low-grade Ni sulphide ultramafic deposits on the recovery of Ni with reference to the grinding and flotation of ores from the Thompson Nickel Belt in Canada. During the development of a flowsheet to process the ores, the occurrence of fibrous chrysotile in amounts close to 1% was detected in the initial drill core samples together with actinolite at concentrations well below 1%. The cyclone overflow slime fraction consisted of floc-like microfibres suspended in the process water and macrofibres were also found in the underflow with some ore samples, indicating that cyclone desliming was effective in removing microfibres but not macrofibres. The presence of a large amount of Mg silicates has the greatest effect on the flotation of pentlandite. A standard test procedure consisting of desliming and rougher and scavenger processing was developed for the ores. The results showed that relatively good Ni recovery was obtained at MgO contents up to 30% but was significantly reduced at higher MgO contents. The presence of fibrous minerals also affects the rheological properties of slurry and may cause problems when discharging the slurry from a rod mill to a flotation cell. The grinding index, which is used to measure the effect of slurry rheology on particle breakage, reaches a maximum at about 60% solids content for the ultramafic ore and then decreases significantly with increasing solids contents. After recovery of the sulphide minerals from the ore, the tailings can be used for CO2 capture since they contain 30%-40% MgO in the form of finely ground slurry., The effect is discussed of the mineralogy of low-grade Ni sulphide ultramafic deposits on the recovery of Ni with reference to the grinding and flotation of ores from the Thompson Nickel Belt in Canada. During the development of a flowsheet to process the ores, the occurrence of fibrous chrysotile in amounts close to 1% was detected in the initial drill core samples together with actinolite at concentrations well below 1%. The cyclone overflow slime fraction consisted of floc-like microfibres suspended in the process water and macrofibres were also found in the underflow with some ore samples, indicating that cyclone desliming was effective in removing microfibres but not macrofibres. The presence of a large amount of Mg silicates has the greatest effect on the flotation of pentlandite. A standard test procedure consisting of desliming and rougher and scavenger processing was developed for the ores. The results showed that relatively good Ni recovery was obtained at MgO contents up to 30% but was significantly reduced at higher MgO contents. The presence of fibrous minerals also affects the rheological properties of slurry and may cause problems when discharging the slurry from a rod mill to a flotation cell. The grinding index, which is used to measure the effect of slurry rheology on particle breakage, reaches a maximum at about 60% solids content for the ultramafic ore and then decreases significantly with increasing solids contents. After recovery of the sulphide minerals from the ore, the tailings can be used for CO2 capture since they contain 30%-40% MgO in the form of finely ground slurry.

El proyecto y las obras que a continuación se describen tratan principalmente sobre la deconstrucción de la cubierta actual de asbesto-cemento del Mercado Central de Abastos de Alicante para proceder a su sustitución por otra de escamas romboidales de zinc, semejante a la original que se ejecutó en 1921 cuando entró en servicio el edificio. Estas obras eran necesarias para evitar las causas (y también las consecuencias) que generan la aparición de filtraciones de agua de lluvia, tal y como quedó descrito en un informe previo que se realizó en 2006, redactado también por el técnico abajo firmante. El artículo muestra las dificultades que representa la aplicación práctica del RD 396/2006 (disposiciones mínimas de seguridad y salud aplicables a los trabajos con riesgo de exposición al amianto) en un caso concreto de una cierta complejidad como es éste, especialmente en aspectos como el económico (incremento de costes), el técnico (aumento de la dificultad de ejecución), y la duración total de la obra (ampliación del plazo total por interferencias con otros oficios)., The project and the works described below mainly deal with the deconstruction of the current asbestos-cement roof of the Central Market in Alicante in order to replace it with another roof of zinc diamond scales, similar to the original which was implemented in 1921 when the building went into service. These works were necessary to avoid the causes (and consequences) that generate the appearance of rainwater infiltration, as was described in an earlier report that was done in 2006, also drafted by the undersigned technician. The article shows the difficulty of the practical application of RD 396/2006 (minimum health and safety requirements for works with risk of exposure to asbestos) in a case of a certain complexity such as this, especially in areas such as economic (rising costs), technical (increasing difficulty of implementation), and the total duration of the work (total time extension due to interference with other trades).

El proyecto y las obras que a continuación se describen tratan principalmente sobre la deconstrucción de la cubierta actual de asbesto-cemento del Mercado Central de Abastos de Alicante para proceder a su sustitución por otra de escamas romboidales de zinc, semejante a la original que se ejecutó en 1921 cuando entró en servicio el edificio. Estas obras eran necesarias para evitar las causas (y también las consecuencias) que generan la aparición de filtraciones de agua de lluvia, tal y como quedó descrito en un informe previo que se realizó en 2006, redactado también por el técnico abajo firmante. El artículo muestra las dificultades que representa la aplicación práctica del RD 396/2006 (disposiciones mínimas de seguridad y salud aplicables a los trabajos con riesgo de exposición al amianto) en un caso concreto de una cierta complejidad como es éste, especialmente en aspectos como el económico (incremento de costes), el técnico (aumento de la dificultad de ejecución), y la duración total de la obra (ampliación del plazo total por interferencias con otros oficios)., The project and the works described below mainly deal with the deconstruction of the current asbestos-cement roof of the Central Market in Alicante in order to replace it with another roof of zinc diamond scales, similar to the original which was implemented in 1921 when the building went into service. These works were necessary to avoid the causes (and consequences) that generate the appearance of rainwater infiltration, as was described in an earlier report that was done in 2006, also drafted by the undersigned technician. The article shows the difficulty of the practical application of RD 396/2006 (minimum health and safety requirements for works with risk of exposure to asbestos) in a case of a certain complexity such as this, especially in areas such as economic (rising costs), technical (increasing difficulty of implementation), and the total duration of the work (total time extension due to interference with other trades).

The main map and six insert maps show producing and past-producing mines, mineral deposits and other claims, permits and licences. Production figures and world rankings for 2008 are tabulated covering niobium, iron ore, manganese, tantalum, bauxite, chrysotile asbestos, magnesite, graphite, vermiculite, kaolin and tin., The main map and six insert maps show producing and past-producing mines, mineral deposits and other claims, permits and licences. Production figures and world rankings for 2008 are tabulated covering niobium, iron ore, manganese, tantalum, bauxite, chrysotile asbestos, magnesite, graphite, vermiculite, kaolin and tin.

Using acid treatment to remove structural cations in the octahedral sites of layered silicate minerals leaves the more stable tetrahedral silica layers to form a porous material. The work described involves the selective leaching of chrysotile with hydrochloric acid and a characterisation of the porous properties and structure of the acid-treated products. The porous silica produced was studied using chemical analysis, FTIR spectroscopy, powder X-ray diffraction and nitrogen adsorption-desorption techniques. It was demonstrated that it retains the nanofibrous morphology of the original chrysotile, and has a high specific surface area of 391.8 m2/g and total pore volume of 1.05 ml/g, reflecting the formation of micropores (1.2-1.5 nm) and mesopores (3.2-3. 8 nm), mainly slit-shaped. The porous silica is amorphous, but its structure is regular to some extent., Using acid treatment to remove structural cations in the octahedral sites of layered silicate minerals leaves the more stable tetrahedral silica layers to form a porous material. The work described involves the selective leaching of chrysotile with hydrochloric acid and a characterisation of the porous properties and structure of the acid-treated products. The porous silica produced was studied using chemical analysis, FTIR spectroscopy, powder X-ray diffraction and nitrogen adsorption-desorption techniques. It was demonstrated that it retains the nanofibrous morphology of the original chrysotile, and has a high specific surface area of 391.8 m2/g and total pore volume of 1.05 ml/g, reflecting the formation of micropores (1.2-1.5 nm) and mesopores (3.2-3. 8 nm), mainly slit-shaped. The porous silica is amorphous, but its structure is regular to some extent.

The molecular structure of the mineral pecoraite, the nickel analogue of chrysotile of formula Ni3Si2O5(OH)4 has been analysed by a combination of Raman and infrared spectroscopy. A comparison is made with the spectra of the minerals nepouite and chrysotile and a synthetic pecoraite. Pecoraite is characterised by OH stretching vibrations at 3645 and 3683 cm-1 attributed to the inner and inner surface hydroxyl stretching vibrations. Intense infrared bands at around 3288 and 3425 cm-1 are assigned to the stretching vibrations of water strongly hydrogen bonded to the surface of the pecoraite. The asbestos-like mineral is charactersied by SiO stretching vibrations at 979, 1075, 1128, 1384 cm-1, OSiO chain vibrations at 616 and 761 cm-1 and Ni-O(H) vibrations at 397 and 451 cm-1.

The processing of chrysotile-asbestos ores prior to concentration is discussed and an ore-blending process described, based on ore grade and size fraction, which has been commercially implemented., The processing of chrysotile-asbestos ores prior to concentration is discussed and an ore-blending process described, based on ore grade and size fraction, which has been commercially implemented.

The Mashaba Igneous Complex (MIC) is a composite, locally well structures and structurally complex ultramafic intrusion emplaced within gneiss and greenstone basement and adjacent greenstone cover rocks. A feature of the regional geology is one of the best-preserved examples of a komatiitic sill in the Zimbabwe craton which contains important chrysotile asbestos deposits. Precise age data are reported for the MIC and a revised geological context for the age data is discussed based on modifications to earlier structural interpretations of the complex., The Mashaba Igneous Complex (MIC) is a composite, locally well structures and structurally complex ultramafic intrusion emplaced within gneiss and greenstone basement and adjacent greenstone cover rocks. A feature of the regional geology is one of the best-preserved examples of a komatiitic sill in the Zimbabwe craton which contains important chrysotile asbestos deposits. Precise age data are reported for the MIC and a revised geological context for the age data is discussed based on modifications to earlier structural interpretations of the complex.

The impact is discussed of exposure to environmental asbestos with particular reference to a study that was carried out in the Haute-Corse department, an area of past asbestos mining where potentially asbestiferous rocks are known in 133 of the 236 communes: the example illustrated is an asbestiform tremolite vein in serpentinised peridotites at Murato, where chrysotile is often associated with tremolite and occasionally with fibres of anthophyllite. The sites of 19 disused mines and asbestos outcrops around France are discussed and noted on a small- scale map. Details are given of a project which will involve the development of a list of naturally occurring asbestos sites, their characteristics and the risk of exposure that they represent. Regulatory aspects of crystalline silica are also briefly noted., The impact is discussed of exposure to environmental asbestos with particular reference to a study that was carried out in the Haute-Corse department, an area of past asbestos mining where potentially asbestiferous rocks are known in 133 of the 236 communes: the example illustrated is an asbestiform tremolite vein in serpentinised peridotites at Murato, where chrysotile is often associated with tremolite and occasionally with fibres of anthophyllite. The sites of 19 disused mines and asbestos outcrops around France are discussed and noted on a small- scale map. Details are given of a project which will involve the development of a list of naturally occurring asbestos sites, their characteristics and the risk of exposure that they represent. Regulatory aspects of crystalline silica are also briefly noted.

In the light of some recent studies on organosilicon derivatives of HCl-leached chrysotile, pioneer works not cited in this area are chronologically and briefly commented, emphasizing the infrared spectroscopy ( FTIR-PAS) characterization of such chrysotile products. The latter have opened a far reaching potential for the development of e.g. highly stable hydrophobic or organophilic materials, including fibrous sheet polymers.

Laboratory and operational investigations of samples from the Dobsina heaps, in the Czech Republic, confirmed that the serpentine waste materal from chrysotile asbestos processing was suitable for hydrometallurgical processing by two-stage hydrochloric acid leaching. The silica and magnesium chloride obtained are suitable for various industrial applications., Laboratory and operational investigations of samples from the Dobsina heaps, in the Czech Republic, confirmed that the serpentine waste materal from chrysotile asbestos processing was suitable for hydrometallurgical processing by two-stage hydrochloric acid leaching. The silica and magnesium chloride obtained are suitable for various industrial applications.

The serpentine waste material in the Dobsina heaps, estimated at 1 300 000 tons of residues from chrysotile asbestos and stoneware production, is suitable as a source of silica and magnesium chloride. Particle size and chemical composition were analysed. Physical processing required before chemical processing includes hydraulic and mechanical sorting, grinding and magnetic separation. Problems to be addressed include removing microfibres and designing closed-circuit continuous grinding., The serpentine waste material in the Dobsina heaps, estimated at 1 300 000 tons of residues from chrysotile asbestos and stoneware production, is suitable as a source of silica and magnesium chloride. Particle size and chemical composition were analysed. Physical processing required before chemical processing includes hydraulic and mechanical sorting, grinding and magnetic separation. Problems to be addressed include removing microfibres and designing closed-circuit continuous grinding.

Some 350 t of gold have been produced from disseminated and lode mineralisation in the Archaean Barberton deposits and more than 200 t from epigenetic mineralisation in the Proterozoic rocks of the Mpumalanga Drakensberg goldfield, the southern portion of which lies within the map area. There is also the producing Nkomati nickel mine and a large part of the dormant Komatipoort coalfield. Substantial tonnages of industrial minerals such as chrysotile asbestos and magnesite have been extracted from mines in the area, as well as lesser amounts of talc and barite. The regional geology is described and a table appended summarising data from 452 economic mineral occurrences and deposits., Some 350 t of gold have been produced from disseminated and lode mineralisation in the Archaean Barberton deposits and more than 200 t from epigenetic mineralisation in the Proterozoic rocks of the Mpumalanga Drakensberg goldfield, the southern portion of which lies within the map area. There is also the producing Nkomati nickel mine and a large part of the dormant Komatipoort coalfield. Substantial tonnages of industrial minerals such as chrysotile asbestos and magnesite have been extracted from mines in the area, as well as lesser amounts of talc and barite. The regional geology is described and a table appended summarising data from 452 economic mineral occurrences and deposits.

Quebec is an important producer of industrial minerals including chrysotile asbestos, titanium products from ilmenite, talc, ground mica, flake graphite, wollastonite and salt. Numerous stone quarries produce crushed rock, dimension stone, limestone for lime and cement, and silica. Peat moss is also extracted. Brucite, chromite, dolomitic magnesite and feldspar were formerly exploited and magnesite, barite and apatite deposits are under evaluation. As well as an overview of industrial minerals in Quebec, papers in this section are on silica resources, exploitation of dimension stone in the Grenville province 1983-1997, and the geology of chrysotile and apatite-ilmenite deposits., Quebec is an important producer of industrial minerals including chrysotile asbestos, titanium products from ilmenite, talc, ground mica, flake graphite, wollastonite and salt. Numerous stone quarries produce crushed rock, dimension stone, limestone for lime and cement, and silica. Peat moss is also extracted. Brucite, chromite, dolomitic magnesite and feldspar were formerly exploited and magnesite, barite and apatite deposits are under evaluation. As well as an overview of industrial minerals in Quebec, papers in this section are on silica resources, exploitation of dimension stone in the Grenville province 1983-1997, and the geology of chrysotile and apatite-ilmenite deposits.