Three fibrous amphiboles that are not regulated as asbestos—two from Biancavilla (Sicily, Italy) and one from Libby (MT, USA)—were studied in order to establish relationships between surface chemistry and surface reactivity. The three fibrous samples, plus one prismatic fluoro-edenite from Biancavilla that was used for comparison, were investigated by X-ray photoelectron spectroscopy (XPS) in order to obtain their quantitative surface compositions and to determine the chemical environment of the Fe in each case. In particular, the Fe 2p3/2 peak was fitted and, for the first for these materials, the binding energies of Fe(II) oxide, Fe(III) oxide and Fe(III) oxyhydroxide were identified. Bulk chemistries and Fe oxidation states were obtained from previous studies for the samples from Biancavilla, and were investigated in the present work by electron microprobe (EMP) and 57Fe Mossbauer spectroscopy (MS) for the sample from Libby. Comparison between surface and bulk data revealed that the sample with the lowest bulk Fe oxidation state was the one most affected by surface oxidation, while the samples with bulk highly-oxidised Fe were showing very high signal of Fe (III) oxy-hydroxide probably due to weathering. The surface reactivities of the fibrous amphiboles were investigated by measuring the production of the [DMPO, HO]• radical adduct using electron paramagnetic resonance (EPR) spectroscopy. Notably, significant chemical reactivity was observed; it was found to be comparable with—or, for the Libby sample, even higher than—that of fibrous tremolite (one of the six asbestos minerals). A positive linear correlation was observed when the production of HO• radical was plotted versus the Fe(II) content on the fibre surface. Data on fibrous tremolite obtained from previous studies were added to substantiate the correlation. These results provide evidence that Fe(II) at the fibre surface controls the production of radicals at the fibre surface. The observed relationship provides further confirmation that Fe topochemistry is strictly related to—though not solely responsible for—the toxicity of asbestos and other fibrous amphiboles that are not regulated as asbestos.

Surface chemistry and surface reactivity of fibrous amphiboles that are not regulated as asbestos.

Amphibole crystals from the former vermiculite mine near Libby, Montana, were examined using three different analytical methods: optical and morphological measurements were made using spindle-stage methods, unit-cell refinements were performed using single-crystal X-ray-diffraction techniques, and chemical analyses were performed using an electron microprobe. The eleven samples display a continuum of morphology and conformity to a single crystal, and range from stubby single-crystal cleavage fragments to elongate near-bundles of fibers. Variations in conformity to the properties of a single crystal are reflected in the character of the X-ray reflections on X-ray rotation photographs. Using current nomenclature recommendations, all of the samples examined consist of winchite. Covariance among several properties was observed. The index of refraction and birefringence are dependent on Mg content. There is also a correlation between birefringence and particle morphology. Winchite particles with a high birefringence and high width/thickness aspect ratio tend to be single crystals, whereas samples with a low birefringence and low width/thickness ratio tend to be more polycrystalline.

Optical, compositional, morphological, and x-ray data on eleven particles of amphibole from libby, montana, u.s.a.

Mineralogy is usually the first geology course taken by students above the 100 level, and as such it is a vital building block for geology curricula. In recent years the number of mineralogists has declined, the relevance of the field has been questioned, and as a result the course has often been taught by less than enthusiastic non-specialists in the field. We believe that the key to restructuring mineralogy involves setting reasonable, prioritized course goals and employing (at least) four modern pedagogical learning methods: spiral learning, inquiry-based learning, concept maps, and use of interactive models and visualization. We present here a revised mineralogy curriculum that benefits from reflections on appropriate content and on these new learning methods and teaching styles.

Integration of New Methods into Teaching Mineralogy

This work concerns the physico-chemical and structural characterisation of mineral fibres (asbestos) and the comprehension of the chemical and molecular mechanisms which are responsible of the development of human pathologies specific to their inhalation. In particular, in this work we performed a crystallochemical and surface reactivity study of floro-edenite, a natural amphibole of volcanic origin recently discovered in Biancavilla (Sicily, Italy). The properties of this mineral were compared to those of other natural mineral fibres, such as tremolite and chrysotile, also present in ophiolitic formations of the Italian peninsula. This work consists of several different parts, which are proof of its multidisciplinary and applied character. In the first part, we studied the mineralogical, chemical and morphological analysis of previously purified natural fibres of fluoro-edenite. The main goal of this part was to determine precisely the crystallographic structure and the composition of this material. This information has been of fundamental importance in the second part of this study, which concerned the toxicochemical properties and the surface reactivity of this mineral. In order to underline the possible pathogenic effect of the inhalation of these fibres, these properties were compared to those of other mineral fibres, such as tremolite and chrysotile, the toxicological properties of which are already known.The second part of this study was finally validated by parallel in vitro and in vivo tests of these materials, in collaboration with a biomedical research group.

Crystal-chemistry and reactivity of fibrous amphiboles of environmental and health interest

Introduction: Over the past year, tremoliteasbestos and vermiculite mining in Libby, Montana have gone from obscurity to the forefront of the national media. The Seattle Post-Intelligencer “broke” the story in November 1999 about the world’s largest vermiculite mine and the problems associated with its asbestos exposure. As the stories point out, several hundred miners, their families, and non-mining residents of Libby were affected, as were thousands of workers in the exfoliation plants where the vermiculite was heated (i.e., exfoliated) into the commercial product Zonolite. Millions of homeowners who have Zonolite in their attics as insulation were also exposed. It now appears that this form of asbestos is one of the most hazardous to date. Why? Geology and mineralogy: The former mine, which was in operation from 1923 to 1990, is located in an altered ultramafic body associated with a Cretaceous age syenite intrusion [1]. The intrusion consists of a ring dike with biotitite in its center surrounded by a biotite pyroxenite, and a pyroxenite with a width of 5-6 km. Some of the biotite is altered to vermiculite and the pyroxenes to amphiboles [2]. Amphibole-asbestos: There have been several studies of the composition of the vermiculite and pyroxenes at the mine [2], but only one analysis of an amphibole [3]. Even though the analysis showed that the amphibole is richterite (formula #1), most workers dealing with these samples still incorrectly refer to them as tremolite. Recently, two more analyses were performed [4] (#2, #3) on samples that turned out to be winchite. K0.32 Na0.31 Na1.08Ca0.92Mg4.57Fe 2+ 1.02Fe 3+ 0.50Mn0.01 Al0.04 Al0.08Si7.92O22(OH)2 #1 K0.13 Na0.16 Na0.72Ca1.25Mg4.25Fe 2+ 0.31Fe 3+ 0.40Mn0.01 Al0.06 Al0.02Si7.98O22(OH)2 #2 K0.14 Na0.27 Na0.67Ca1.33Mg4.43Fe 2+ 0.13Fe 3+ 0.37Mn0.04 Al0.01 Al0.06Si7.94O22(OH)2 #3 K0.20 Na0.00 Na1.16Ca0.84Mg3.86Fe 2+ 0.28Fe 3+ 0.72Mn0.02Ti0.03 Al0.10 Al0.08Si7.92O22(OH)2 #4 K0.26 Na0.11 Na1.02Ca0.98Mg3.81Fe 2+ 0.21Fe 3+ 0.49Mn0.02Ti0.05 Al0.29 Al0.00Si8.00O22(OH)2 #5 K0.21 Na0.02 Na0.95Ca1.05Mg4.11Fe 2+ 0.18Fe 3+ 0.56Mn0.01Ti0.03 Al0.11 Al0.02Si7.98O22(OH)2 #6 We have analyzed three more samples (#4-#6) and also found them to be winchite. Fe/Fe values in #1 are from wet chemistry, and in #2-#6 are by Mossbauer spectroscopy. These analyses assume that all the Fe in the samples is in the amphibole; however preliminary low temperature data suggest the possible presence of a very fine-grained (100 A scale) ferric oxide impurity. Winchite and richterite are not among the six regulated asbestos minerals. Clearly they should be, and ALL amphibole-asbestos should be regulated (i.e., we should regulate based on group and not species names). Amphibole-asbestos: But what is asbestos? Surprisingly, this question still does not have a good answer. Based on current OSHA regulations, any of the five regulated amphiboles (crocidolite, amosite, tremolite, actinolite and anthophyllite) are considered asbestos if they have an aspect ratio (i.e., length to width) of >3 and are >5 μm in length. In 1992, OSHA deregulated cleavage fragments regardless of their aspect ratio, based on health effects studies showing differences between fibers and fragments [5]. The table below gives particle counts for samples #4-#6 for approximately 900 particles using a polarized light microscope. We found that the samples were about 1/3 fibers (i.e., asbestos), 1/3 fragments and 1/3 undeterminable. #4 #5 #6 NIST

B. M. Brown

Papers

Amphibole-Asbestos, Vermiculite Mining and Libby, Montana: What's in a Name?