Vermiculite

This series of articles should provide ample background to the story of vermiculite. It has served as a valuable commercial product over time, and continues to be mined, processed, and utilized around the world. For many years, vermiculite has been appreciated for its physical and chemical properties. Its physical properties, which allow expansion to a light density particle, make it suitable for light aggregate in concrete and other building materials and low heat transfer effective for insulation. The chemical properties which include an active cation exchange surface are ideal for agricultural products. Its natural formation is a micaceous mineral, composed of flat crystal plates arranged in a multi-laminate stack. Of great misfortune is the association of some vermiculite deposits with asbestiform amphibole formations. A remote Montana vermiculite deposit cohabitated with a large formation of these asbestiform minerals. Further complicating the situation is that this vermiculite deposit near Libby, Montana, produced a large majority of the world supply during the sixty-seven years of operation resulting in wide distribution of contaminated vermiculite. The epicenter of mining and processing was an isolated town where ongoing occupational and environmental exposures spanned throughout the years of mining operations. Morbidity and mortality studies recognize the pervasive adverse effects from amphibole exposure, not just in Libby, Montana, but also at export sites processing the vermiculite ore. Being the first population exposed to the unstudied asbestiform amphiboles winchite and richterite, there has been significant advancement in understanding their induced health effects. Studies in the toxicology of fibrous amphiboles and human health studies where a different pattern of asbestos-induced disease has been observed with Libby amphibole asbestos exposure have been completed. The observations have broadened our understanding of Libby amphiboles and enlightened us to the hazards of environmental exposure, and the long-term public health risk from existing contaminated vermiculite.

Aggregates and naturally occurring asbestos: the need of a correct analytical approach

<p>Aggregates (sand, gravel and crushed stone) characterized by good mechanical properties and no undesired reactivity, are used in huge amounts in many industrial sectors, especially in construction (e.g. concrete, asphalt, paving). Sand and gravel extracted from alluvial or glacial deposits are typically rounded and well selected, whereas crushed stone is angular and suitable for certain applications (e.g. railway ballast). Use of offshore deposits is mostly restricted to beach erosion control and replenishment. Demand for aggregates is governed essentially by markets, and sources of supply need to be situated close to each other, because of transportation costs. The most common rock types (depending on geology) are represented by basalts, porphyries, orthogneisses, carbonatic rocks and “green stones” (serpentinites, prasinites, amphibolites, metagabbros). Especially “green stones” may contain traces, and sometimes appreciable amounts of asbestiform minerals (chrysotile and/or fibrous amphiboles). For example in Italy, the chrysotile asbestos mine in Balangero (Turin) produced over 5 Mt railroad ballast (crushed serpentinites), which was used for in northern and central Italy, from 1930 up to 1990. The legal threshold for asbestos content in track ballast is established in 1000 ppm: if the value is below this threshold, the material can be used, otherwise it must be disposed of as hazardous waste, with very high costs. The presence of asbestiform minerals must be first assessed by preliminary geological and mineralogical surveys in quarry areas, both for glacial – alluvial deposits and “massive” rock mass (crushed stone). The quantitative asbestos determination in rocks is a very complex analytical issue: although techniques like TEM-SAED and micro-Raman are very effective in the identification of asbestos minerals, a quantitative determination on bulk materials is almost impossible or expensive and time consuming. Another issue is represented by the discrimination of asbestiform minerals (e.g. chrysotile, asbestiform amphiboles) from the common acicular – pseudo-fibrous varieties (lamellar serpentine, non-asbestiform amphiboles). Also, the correct sampling is of crucial importance, considering the size of rock fragments (sand, gravel or silt) and the geological variability within the quarry. In this work, more than 400 samples from the main Italian quarry areas were characterized by a combined use of XRD and an up to date sample preparation and quantitative SEM-EDS analytical procedure. The first step consists in the recognition of “green stones” (presence of serpentine and/or amphiboles) by means of macroscopic petrography (gravel) or XRD (sand, silt). The second step is represented by the “self-grinding” of the rock fragments (Los Angeles rattle test for gravel), and the quantitative SEM-EDS analysis of the “fine” fraction (< 2 mm). The third and last step consists in the complete grinding of the bulk sample and following SEM-EDS quantification. The results show a great variability for serpentinite-rich samples, with a wide asbestos concentration range; on the other hand, metabasites (prasinites, amphibolites) are generally less critical, because the presence of asbestiform amphiboles (especially tremolite - actinolite) is rarer and more occasional. As regards the samples deriving from alluvial and glacial deposits, the fibers tend to concentrate in the fine fraction (<2 mm).</p>

High tremolite asbestos content in urine related to dispersion from NOA rocks: a case study

<p>The naturally occurring asbestos (NOA) and naturally occurring of asbestiform minerals non asbestos classified (NONA) in North Western Italian Alps is known since many years and described in a few papers (e.g., Belluso et al., 1995; ARPA Piemonte, 2008). Whereas the noxiousness due to professional exposure to asbestos is well known, there are few information dealing with natural environmental exposure as that occurring to general population living closeness to NOA (and NONA) in outcropped rocks.</p><p>The investigation of inorganic fibres content in urine may understand if people respired them in the latest period (from several days to some months: e.g., ATSDR, 2001).</p><p>In this study we present a case of a very high and abnormal content of tremolite asbestos detected in urine of a young girl during a survey of several toxic contaminants respired from young students in a Turin province school (NW Italy).</p><p>The absence of asbestos revealed by further investigation carried out in urine sample of girl’s parents and in other samples from the girl, showed that the high asbestos content previously detected was due to an exposure occurrence limited in time and related only to the girl.</p><p>The investigation carried out on the lifestyle of the girl in the year preceding the urine analysis allowed to suppose that the detected high content of tremolite asbestos might be due to a specific environmental exposure. Indeed, the girl spent a holiday period away from her habitual home, where there were excavation works in NOA rocks spotty containing important amount of tremolite asbestos. Therefore, the asbestos detected in the urine is probably connected to those dispersed from NOA rocks.</p><p>This finding focuses on the need to evaluate the risk of asbestos air dispersion from NOA rocks before carrying out excavation works.</p><p> </p><p>ARPA PIEMONTE (2008) Amianto naturale in Piemonte. Agenzia Regionale per la Protezione Ambientale del Piemonte, ARPA Piemonte, Ed. L’Artistica Savigliano (CN), I</p><p>ATSDR, Agency for Toxic substances and Disease Registry (2001). U.S., Department of Health and Human Services, Public Health Service. Atlanta, GA, USA</p><p>BELLUSO E, COMPAGNONI R, FERRARIS G. (1995) Occurrence of asbestiform minerals in the serpentinites of the Piemonte Zone, Western Alps. In: Giornata di studio in ricordo del Prof. Stefano Zucchetti, Politecnico di Torino, 57-64. Ed. Politecnico di Torino, I</p>

Asbestiform Minerals of the Franciscan Assemblage in California with a Focus on the Calaveras Dam Replacement Project

ABSTRACT The San Francisco Bay Area is underlain by bedrock of the Franciscan Assemblage, which outcrops in numerous places. A significant portion of these outcrops consists of rock types that contain both regulated and unregulated asbestiform minerals, including ultra-mafic serpentinites, various greenstones, amphibolites, blueschist, and other schists (talc-tremolite, actinolite, etc.). These rocks are a legacy of tectonic activity that occurred on the west coast margin of the North American plate ∼65–150 MY ago during subduction of the East Pacific and Farallon plates. The Calaveras Dam Replacement Project (CDRP), located in Fremont, California, is an example of an area within the Franciscan Assemblage that is substantially underlain by metamorphosed oceanic sedimentary, mafic, and ultra-mafic rocks in a tectonic subduction zone mélange with highly disrupted relationships between adjoining rock bodies with different pressure/temperature metamorphic histories. In order to protect the health of workers and residents in the surrounding area, an extensive effort was taken to identify, categorize, and monitor the types, locations, and concentrations of naturally occurring asbestos at the site. Using a combination of geologic field observations and transmission electron microscopy, energy dispersive X-ray, and selected area electron diffraction analysis of airborne particulate and rock/soil samples, the CDRP was discovered to contain chrysotile-bearing serpentine. It also had as a range of amphibole-containing rocks, including blueschist, amphibolite schist, and eclogite, with at least 19 different regulated and non-regulated fibrous amphibole minerals identified. The extensive solid solution behavior of the amphiboles makes definitive identification difficult, though a scheme was created that allowed asbestos mineral fingerprinting of various areas of the project site.

Naturally Occurring Asbestiform Minerals in Italian Western Alps and in Other Italian Sites

ABSTRACT The natural occurrence of asbestos (NOA) in rocks and soil has been known for many years in several areas of the world, differently from the natural presence of asbestiform minerals. In Italy, the mapping of NOA is mandatory according to the 2001 and 2003 regulations. An investigation, not yet concluded, has revealed that in Italy, NOA is represented by chrysotile and tremolite asbestos with minor amounts of actinolite asbestos and anthophyllite asbestos. A field survey conducted in the Italian Western Alps (IWA), dealing with the natural occurrence of asbestiform minerals non-asbestos classified and not regulated, started many years ago and is still ongoing. It revealed that the following kinds of asbestiform silicates are present (in decreasing order of frequency): asbestiform polygonal serpentine and asbestiform antigorite, asbestiform diopside, asbestiform carlosturanite, asbestiform forsterite, asbestiform sepiolite, asbestiform balangeroite, and asbestiform talc. The asbestiform non-silicates brugnatellite and brucite have been rarely detected. Outside the IWA, asbestiform zeolite (erionite and offretite), asbestiform sodium amphibole (fluoro-edenite), and a few other asbestiform silicates have been also detected. For some asbestiform minerals, the identification is problematic and needs the use of transmission electron microscopy combining imaging at high magnification and electron diffraction and chemical data. This investigation is particularly important to distinguish four kinds of asbestiform minerals (antigorite, polygonal serpentine, carlosturanite, and balangeroite) from chrysotile since only the last one is regulated. The issue is much more complicated by the intergrowth of different fibrous species on the submicrometer scale.

Micro-Raman Spectroscopy, a Powerful Technique Allowing Sure Identification and Complete Characterization of Asbestiform Minerals

Micro-Raman spectroscopy has been applied to fibrous minerals regulated as “asbestos”—anthophyllite, actinolite, amosite, crocidolite, tremolite, and chrysotile—responsible of severe diseases affecting mainly, but not only, the respiratory system. The technique proved to be powerful in the identification of the mineral phase and in the recognition of particles of carbonaceous materials (CMs) lying on the “asbestos” fibers surface. Also, erionite, a zeolite mineral, from different outcrops has been analyzed. To erionite has been ascribed the peak of mesothelioma noticed in Cappadocia (Turkey) during the 1970s. On the fibers, micro-Raman spectroscopy allowed to recognize many grains, micrometric in size, of iron oxy-hydroxides or potassium iron sulphate, in erionite from Oregon, or particles of CMs, in erionite from North Dakota, lying on the crystal surface. Raman spectroscopy appears therefore to be the technique allowing, without preparation of the sample, a complete characterization of the minerals and of the associated phases.

QUANTITATIVE ANALYSIS OF ASBESTOS FIBRES IN OPHIOLITIC ROCKS USED AS AGGREGATES AND HAZARD RISK ASSESSMENT FOR HUMAN HEALTH

This study focuses on the quantification of asbestiform minerals in basic and ultrabasic rocks from ophiolite suites of central and northern Greece. A combination of different methods were used for the detailed investigation of the samples, conducted in the following stages: (i) petrographic examination of thin sections with a polarizing microscope, (ii) mineral phase analysis using X-ray diffraction, (iii) determination of the fibrous mineral composition on polished thin sections using scanning electron microscopy, (iv) image analysis of back scattered electron images and secondary electron images, to quantify the dangerous asbestiform crystals. SEM is proved to be the most powerful tool for the detailed investigation of fibrous minerals, although polarized microscopy and XRD are necessary tools for a preliminary identification of these minerals. Basic rocks contain various amounts of actinolite, however not all crystals comprise asbestiform fibres. A conspicuous feature observed during careful petrographic analysis is that many of the non as best form actinolite crystals are broken up along their cleavage planes. Rocks with such features need specific consideration since these crystals may subsequently release numerous fibrous cleavage fragments during the production processes and in-service deterioration of aggregates. Among the serpentinized ultrabasic samples, only one contains chrysotile, while the other samples contain antigorite and lizardite.

5. Minerals and the living world

‘Minerals and the living world’ considers various mineral–microbe interactions, biomineralization, and how minerals interact with the human body and human health. Biomineralization is the process where living organisms produce minerals such as calcite, apatite, and silica. An example is the unicellular, ocean-living radiolaria that have complex silica skeletons. After death their skeletal remains sink to the ocean floor and can be seen preserved in cherts and flints. Human biominerals can be divided into those which are an essential part of the bodies’ systems, such as hydroxylapatite found in bones and teeth, and those which are unexpected and pathological mineral deposits, such as calcium oxalate and asbestiform minerals.