McGrath, M., L. Li, M.S. Sanchez, D.R. Van Orden, R.J. Lee, Characterization of Structurally Coherent Mineral Intergrowths in Cosmetic Talc, 2015 GSA Annual Meeting Baltimore, MD., Geological Society of America, Vol. 47, pp. 759, 2015.
Recent allegations claim that historic and current commercial talc products contain asbestos. A number of samples have been examined after claims were made that these samples contain asbestiform amphiboles. These allegations are the result of misidentification due to misunderstanding of the mineralogy and crystallography of amphiboles and talc. The complex microstructures involving the biopyriboles and their structural relationships were first characterized by Veblen and others 35 years ago. The particles analyzed herein were prepared according to standard bulk powder testing employed for asbestos testing by TEM. These mounts are not ideal as they produce semi-random particle orientations and thus double tilting and or rotate tilt methods are required for characterization. In this paper, we summarize the results of detailed selected area diffraction experiments and compare those results with simulated diffraction patterns from particles that are misidentified as amphibole. However these particles are topotaxial intergrowths of talc and anthophyllite and/or talc and tremolite. These intergrowths are recognized in coherent reactions where bampequals btalc and camp equals atalc.
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