Mineralogical and dimensional characterization of EMPs destined for biological experimentation

Mineral specimens and mineral reference materials should be understood to be mixtures of various mineral species and the properties of each individual species will likely represent a range of quantifiable values and qualitative characteristics. The use of incompletely characterized mineral specimens may introduce significant uncontrolled variables in any experiment. Any mineral characterization should include an understanding of the bulk properties of the specimen as well as microanalytical and crystallographic characterization of individual mineral phases. This characterization should comprise a range of length scales to accommodate naked-eye level observations up to electron microscopic observations and analyses. Large spatial scale observations are useful to describe the physical properties of the material and understand the scale of inhomogeneities that may be present in a mineral sample. Microanalysis provides critical compositional and crystallographic information for mineral identification. It is critical to recognize where gaps might exist in the data produced during the characterization of a material and if those gaps are critical to evaluating the effect those minerals might have on the result of a given experiment. Likewise, it is critical to understand the interplay of various minerals that might be present in a sample other than the specific mineral of interest. The accessory minerals that are present, even if only trace amounts, could have a major impact and need to be isolated, or their impact accounted for in the interpretation of results. Dimensional characterization of particulate produced from a mineral specimen is important, but not as simple a task as it might appear. Dimensional data can be produced through any of several microscopic techniques, each with specific limitations and potential to be biased due to sample preparation technique. This understanding of the full composition of a mineral specimen cannot be obtained through rudimentary examination and it cannot be taken for granted that it has been performed by the supplier of the specimen.

Scanning electron microscopy and transmitted electron backscatter diffraction examination of asbestos standard reference materials, amphibole particles of differing morphology, and particle phase discrimination from talc ores

Since 1972, when the US Occupational Health and Safety Administration established the first limits on occupational exposure to asbestos fibers, numerous analytical methods employing several microscopy techniques have been developed to identify a group of minerals defined by legislation as asbestos. While transmission electron microscopy (TEM) is implemented in standardized analytical methods, these methods specify the use of selected area electron diffraction. Because of this constraint, the diffraction data a TEM can provide are often underutilized due to challenges associated with collecting and interpreting individual diffraction patterns. It has been shown that transmission electron backscatter diffraction (tEBSD) produces diffraction patterns nearly identical to electron backscatter diffraction, but from smaller crystal domains. This paper explores the utility of tEBSD for characterization of asbestiform particles from reference asbestos materials, a suite of amphibole minerals of varying morphologies to determine if there is a correlation between mineral habit (i.e., crystal form), microscopic particle shape preferred orientation, and mineral specimens from an industrial talc deposit to provide a case study of the utility and limitations of the technique.

A review of scientific literature examining the mining history, geology, mineralogy, and amphibole asbestos health effects of the Rainy Creek igneous complex, Libby, Montana, USA

This article reviews the past 90 yr of scientific research directed on multiple aspects of the unique geology and environmental health issues surrounding the vermiculite deposit found at Libby, MT. Hydrothermal alteration and extensive weathering of the ultramafic units resulted in the formation of a rich deposit of vermiculite that was mined for 67 yr and used in numerous consumer products in its expanded form. Later intrusions of alkaline units caused hydrothermal alteration of the pyroxenes, resulting in formation of amphiboles. Some of these amphiboles occur in the asbestiform habit and have been associated with pulmonary disease in former miners and mill workers. Identification of these amphibole asbestos minerals has received little attention in the past, but recent work shows that the majority of the amphibole mineral species present may not be any of the amphibole species currently regulated by government agencies. Epidemiological studies on former miners have, nevertheless, shown that the amphibole asbestos from the Rainy Creek igneous complex is harmful; also, a recent study by the Agency for Toxic Substances and Disease Registry shows that residents of Libby who had not been employed in the vermiculite mining or milling operations also appear to have developed asbestos-related pulmonary diseases at a higher rate than the general public elsewhere. Since November 1999, the U.S. Environmental Protection Agency has been involved in the cleanup of asbestos-contaminated sites in and around Libby associated with the mining and processing of vermiculite.