Characterization of talc and associated minerals

Our plain-English summary of Characterization of talc and associated minerals, by D.H. Hamer, F.R. Rolle, J.P. Schelz (American Industrial Hygiene Association Journal, 1976).

The study

• Authors: D.H. Hamer, F.R. Rolle, J.P. Schelz
• Journal: American Industrial Hygiene Association Journal
• Published: 1976;37(5):296-304
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002286).

Abstract

The unequivocal identification of mineral impurities in talc requires definitive analytical techniques due to the very similar structure of many naturally occurring silicates and the small quantities of associated minerals frequently found. The instrumental methods and techniques extant for this purpose are reviewed. Light microscopy, x-ray diffractometry, and differential thermal analysis have been found to be particularly useful, complementary, and practical for both exploratory and routine determinations of mineral impurities in the talc matrix. When necessary, transmission electron microscopy is recommended for the analysis of mineral components present at sub-trace levels.

In plain English

This 1976 article, by three authors from the Analytical Laboratories of Johnson & Johnson, was a review of laboratory methods for identifying mineral impurities in talc, mainly cosmetic talc. It did not study people. The authors distinguished three meanings of talc: the pure mineral, cosmetic talc (normally more than 90% talc) and industrial talc (often less than 50% talc). They described light microscopy, dispersion staining, scanning and transmission electron microscopy, x-ray diffraction and thermal analysis, along with drawbacks of each. For example, they wrote that experts using light microscopy in an industry "round robin" test failed to agree on results. They reported that thermal analysis could detect carbonate minerals at levels of less than 0.5% by weight. The authors stated that several years of examining commercial cosmetic talc had failed to confirm earlier allegations of chrysotile asbestos; this article presents no data for that statement. They concluded that light microscopy, x-ray diffraction and differential thermal analysis were useful together for routine analysis, and that transmission electron microscopy may be needed for very small particles.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: review of analytical methods for identifying minerals in talc
• Who was studied: No people were studied. The subject was talc and its associated minerals, mainly cosmetic talc. The authors were from the Analytical Laboratories of Johnson & Johnson, New Brunswick, N.J.
• Exposure: Mineral impurities in talc, in the context of claims of asbestos in talc. Chrysotile asbestos is named as an alleged contaminant. Other minerals named are chlorite, magnesite, calcite and dolomite at minor levels, and phlogopite, muscovite, quartz, rutile and iron oxide at trace levels (less than 1%).
• Main results:
  • The authors described cosmetic talc as normally containing more than 90% talc.
  • The authors described industrial talc as a very impure product that often contains less than 50% talc.
  • The authors reported that in a cosmetic industry round robin talc analysis using light microscopy, a number of experts failed to agree on the results.
  • The authors stated that dispersion staining cannot work with particles much less than about five micrometers in size.
  • The authors described transmission electron microscopy as extremely time-consuming, because many grids and fields must be examined for statistically valid results.
  • According to the authors, differential thermal analysis can detect carbonate minerals in talc at levels of less than 0.5% by weight.
  • The authors reported that no two talc samples mined from different locations gave the same thermal analysis curve, while samples from one mine over time gave almost identical curves.
  • The authors stated that several years of examining commercial cosmetic talc supplies from domestic and foreign sources had failed to confirm earlier allegations of chrysotile asbestos. No supporting data are presented in this article.
• The authors' conclusion: The authors recommended a routine scheme with three steps. First, light microscopy. Second, combined x-ray diffraction and differential thermal analysis. Third, dispersion staining if doubt remains, with transmission electron microscopy and selected area electron diffraction when single or very small particles must be identified.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: Talc, Silicate, Transmission Electron Microscopy (TEM).

Related studies

• Consumer talcums and powders: mineral and chemical characterization — A.N. Rohl, A.M. Langer, et al. (1976)
• Identification of chlorite and serpentine in cosmetic or pharmaceutical talc — A.M. Blount, A.H. Vassiliou (1983)
• Mineralogical features associated with cytotoxic and proliferative effects of fibrous talc and asbestos on rodent tracheal epithelial and pleural mesothelial cells — A.G. Wylie, H.C. Skinner, et al. (1997)
• A review of mortality associated with elongate mineral particle (EMP) exposure in occupational epidemiology studies of gold, talc, and taconite mining — J.H. Mandel, B.H. Alexander, et al. (2016)
• Physicochemical characterization of cryogenically ground, size separated, fibrogenic particles — P.S. Thorne, E.N. Lightfoot, et al. (1985)
• Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres — G. Monchaux, J. Bignon, et al. (1981)

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