INITIAL ANALYSIS OF SOME HISTORIC TALC PRODUCTS: ELECTRON MICROSCOPY INVESTIGATION OF MINERALOGICAL IMPURITIES

Talc is a hydrous phyllosilicate that is commonly used in a wide range of commercial mineral products. Most talc used in commercial products has been mined primarily in carbonate meta-sedimentary hosted deposits such as in China and Montana, and hydrothermal alteration deposits of mafic and ultramafic rocks, such as ophiolitic rocks in Vermont. Owing to physical and chemical aspects of mineral stability and the geologic setting of both carbonate meta-sedimentary hosted deposits and mafic and ultramafic rock hosted deposits, a variety of asbestos contaminants and metal contaminants have the potential to occur in derived commercial talc products. The nature and variability of asbestos, minerals, and other contaminants in commercial talc products are unclear. Transmission electron microscopy and scanning electron microscopy was used to investigate an initial small suite of commercial talc products spanning from 1960 to 2019 using simple grain mount sample preparation techniques. Electron microscopy collectively indicates that impurities of several different types occur in talc products. These include Fe-Ti-oxides, pyrite, calcium phosphate, and different fiber types. Nickel was observed in minor quantities in talc in a product from 1985 using both transmission electron microscopy – energy dispersive spectroscopy analysis and scanning electron microscopy – energy dispersive analysis. Nickel concentrations observed in this commercial product sample are consistent with natural talc samples from a possible source location in Vermont. Findings are broadly consistent with other published studies on mineral contaminants in commercial talc products as well as previous work in our lab. Results indicate concern for impurities is warranted in these talc products. To further understand the implications of these preliminary findings, more work will need to be completed to evaluate potential variation with respect to mineral diversity and chemical composition of minerals within individual bottles of product, among multiple bottles of the same product, and among source locations for products. Such evaluations ideally should be done from samples over several periods of time.