The Near and InterMediate Range Order Diffractometer (NIMROD) was used to examine the potential impact of shale mineralogy on CO2 behavior within micropores. Two samples with varying mineral compositions were obtained from producing intervals in the dry gas window in the Middle Devonian Marcellus Shale. One of the samples contained relatively high amounts of quartz and clay and low carbonate, the other contained relatively equal amounts of quartz, carbonate, and clay. The samples were probed with CO2 at subcritical pressures (20–50 bar) and temperature (22 °C) and characterized over a neutron scattering vector (Q) range of 0.02 < Q < 50 Å–1. This Q range provides information from the atomistic length-scale up to pore radii of 10 nm. Mineralogy variations between the samples did not affect scattering ratios over the entire Q range accessible with the NIMROD. Q values for the minimum scattering ratios of both samples at similar pressures are remarkably similar, particularly for Q < ∼0.09 Å–1, and maximum scattering ratios are similar in both samples suggesting that mineral pores are so uncommon in the pore sizes examined that they cannot be resolved due to the overwhelming amounts of organic pores in these samples. Overall, these findings suggest that mineralogical variations have little effect on CO2 behavior within organic matter-hosted shale micropores at high thermal maturities and they lend support to the assertion that CO2 cannot be stored in the vast surface areas of micropores in organic material in shale formations. In addition, CO2 enhanced oil recovery (EOR) is unlikely to displace petroleum from some of the smaller mesopores (2.5 to ∼3.5 nm) and all of the micropores because they are effectively closed to CO2.

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.

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.

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Three natural amphibole samples collected from the former vermiculite mine near Libby, Montana, USA, have been analysed by Rietveld X-ray powder diffraction (XRPD) refinement and Fourier transform infrared spectroscopy (FTIR) in the OH-stretching region. The same materials have been analysed previously by electron microprobe analysis (EMPA), Mössbauer spectroscopy and structure refinement (SREF) single crystal X-ray diffraction (SC-XRD), which revealed that these amphiboles have a crystal chemical formula very close to an intermediate composition between winchite and richterite, i.e. A A 0.5 B NaCa C Mg 4.5 M 3+ 0.5 T Si 8 O 22 (OH) 2 (A = Na and/or K; M 3+ = Fe 3+ and/or Al). The Rietveld analysis showed the powder samples used for the experiments here to be composed only of amphibole. This in turn allowed us to use FTIR OH-stretching data to derive cation ordering on these powder samples. The three FTIR spectra are quite similar and up to four components can be fitted to the patterns. The two lower-frequency components (labelled A and B) can be attributed to a local O(3)ÀH dipole surrounded by M(1)M(3) Mg 3 and M(1)M(3) Mg 2 Fe 2+ (respectively), an empty A site and T Si 8 environments; on the contrary, the higher-frequency C and D bands indicate the presence of an occupied A site. The FTIR OH-stretching data alone allow us to calculate the site occupancy of the A, M(1)ÀM(3) and T sites with confidence, as compared with previously published data. By contrast M(4)-and M(2)-site occupancies are more difficult to evaluate. This study takes advantage of the large database of well characterized synthetic amphiboles, built over the last two decades. The comparison of vibrational spectroscopy data with micro-chemical and crystallographic data reported in this study demonstrate that the FTIR OH-stretching method alone is a valuable and rapid method to derive or at least sensibly constrain site occupancy for natural amphiboles. A much more detailed cation site occupancy can be obtained by combining micro-chemical and FTIR OH-stretching data.