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We obtained oriented Fe-XANES spectra on three amphibole bundles of fiber (i.e., asbestiform morphology), two single-crystal fragments (i.e., nonasbestiform morphology), and one aggregate of thousands of smaller particles (termed herein a "puffball") by use of a spindle stage mounted on beamline X26A, National Synchrotron Light Source, Brookhaven National Lab. These particles of differing morphology were obtained from a single rock sample collected at the former vermiculite mine near Libby, Montana, U.S.A. The XANES spectra vary as a function of orientation for the single- crystal fragments and bundles of fibers and were the same regardless of orientation for the puffball. Differences in the spectra for the single-crystal fragments and bundles of fibers indicate variations in Fe oxidation states between the two differing morphologies. Comparison to a calibration line based on amphibole standards allowed determination of Fe3+/∑Fe values of 0.69 for the bundles of fibers and 0.60 for the single-crystal fragments, while the puffball had a Fe3+/∑Fe value of 0.66. These values agree well with our earlier Mössbauer data on a bulk sample of this same material, with Fe3+/∑Fe of 0.65. To our knowledge, these are the first data that show compositional differences between asbestiform and nonasbestiform amphiboles from the same sample. Because health effects appear to vary with amphibole morphology, these results suggest that iron oxidation, mineral morphology, and potential health effects may all be interrelated. [ABSTRACT FROM AUTHOR]

Compositional data and Fe&sup3+;/ΣFe ratios obtained by electron microprobe and Mössbauer analyses are given for a suite of three amphibole and amphibole-asbestos samples collected from the former vermiculite mine near Libby, Montana. A crystal structure analysis, compositional data, and Fe&sup3+;/ΣFe values for two samples from a previous study are also reported. The results confirm the conclusion drawn in the previous study that these amphiboles are dominantly compositions ranging from winchite to richterite. Mössbauer spectroscopy yielded Fe&sup3+;/ΣFe ratios from 58% to 72% for the five samples. The crystal structure was determined for a single crystal selected from a bulk sample. Its formula (as determined by electron microprobe analysis and Mössbauer spectroscopy) is (K[sub0.19] Na[sub0.32])[subA](Na[sub0.85] Ca[sub1.12]Mn[sub0.03])[subB](Mn[sub0.01]Mg[sub4.43]Feb[sup.3+, sub0.34]Fe[sup2+, sub0.19]Ti[sub0.01]Al[sub0.02]) Al[sub0.03]Si[sub7.97]O[sub22])(OH[sub1.63]F[sub0.37]). The refinement was carried out based on space group C2/m, with a = 9.879(2), b = 18.024(3), c = 5.288(1 ) Å β = 104.377(3)° and using data collected at room temperature. Mg is partitioned among the M1, M2, and M3 sites. All of the Fe&sup3+; occupies M2, while Fe&sup2+; is split between M2 and M3; Ca and Na fill the M4 site, while Na and K occupy the partially filled A site. The A-site occupancy is calculated as 0.51 based on chemical data, but only 0.48 based on X-ray diffraction results. Minerals with the former values would be classified as richterite and those with the latter as winchite. [ABSTRACT FROM AUTHOR]