INITIAL MINERALOGICAL AND GEOCHEMICAL EVALUATION OF TALC CRAYONS FROM CHINA

Talc products are of broad community interest within the contexts of both consumer and occupational exposure to asbestos and toxic metals. In the past several decades, crayons (often marketed towards children) have been found to contain fibrous tremolite in trace amounts. One talc-based product that has not been investigated in detail is talc crayons specifically used for marking in manufacturing. In this study, an unopened box of talc-based industrial crayons originating from China were analyzed for their mineralogical and chemical properties. Twenty crayons were manually powdered and first examined using basic powder X-ray diffraction (XRD). Powdered splits of all twenty crayons were analyzed for their bulk elemental chemistry via inductively coupled plasma mass spectroscopy (ICP-MS) and select samples were analyzed with scanning electron microscopy (SEM). XRD results indicates that talc is the primary component of the crayons and extreme mineralogical variation (e.g., in calcite or dolomite) is lacking. From ICPMS, potentially hazardous elements V, Ni, Cr, and Co were low in concentration with averages of a few parts per million (ppm). Ca concentrations and P are highly correlated (r² = 0.978) and rare earth elements (REEs; e.g., Y, Ce,) are also highly correlated with Ca. Both Fe and Al are common and are present at average concentrations of 4106 ppm and 1370 ppm respectively. Sample study via SEM indicates the presence of some potentially countable particles consistent with tremolite that occur in the talc matrix material with dimensions of 200 nm x 650 nm. SEM also indicates that Fe is present in some talc particles. These initial findings suggest that these talc-based products may have a distinct geochemical fingerprint and should be further evaluated for asbestos content. Preliminary results indicate that there appears to not be significant concentrations of many elements of environmental or occupational concern, however the occurrence of asbestos in these products is an open question and will be investigated further. Asbestos is well understood and documented to cause mesothelioma, and while research exists which focuses on cosmetic products, attention should also be given to other commercial or industrial materials to provide mineralogical and geochemical context for health professionals.