Status of the reference X-ray powder-diffraction patterns for the serpentine minerals in the PDF database - 1997

A critical examination of the reference X-ray powder-diffraction patterns o f the serpentine minerals in the Powder-Diffraction File (PDF) database has revealed an unsettling situation. Most of the patterns in, or previously i n, the PDF database are inaccurate, misidentified, or of poor quality. The PDF database is not a dependable tool for identifying the serpentine minera ls, and has not been since the mid-1960s. This has serious implications for studies on serpentine minerals that have depended on the PDF database, par ticularly those by nonmineralogists doing health and environmental studies of chrysotile asbestos. In the current PDF database, lizardite-1T, carlostu ranite. some amesite, and possibly some antigorite (but with inappropriate polytype symbols) can be identified. Only one of the many multilayer lizard ites can be identified. The current pattern for chrysotile-2M(c1) (clinochr ysotile) is of reasonable quality, but not the best, however the earlier pa tterns still in the database are so problematic that any chrysotile-2M(c1) identification must be considered suspect. Chrysotile-2O(c1) (orthochrysoti le), and any mixture of serpentines cannot be identified using the PDF data base. Until the reference serpentine patterns art: corrected the PDF databa se cannot be considered a reliable identification tool. High-quality powder -diffraction patterns of the serpentine minerals have been published and ca n be rapidly introduced into the PDF database. (C) 2000 International Centr e for Diffraction Data. [S0885-7156(99)00503-5].