December 30, 2003

Analytical Science

Sampling and Analysis of Crude Vermiculite Samples
For Possible Asbestiform Fibre and Quartz Content

PROJECT NO: 609-00324(610)


    Palabora Europe Limited is the European distributors of vermiculite produced by the Palabora Mining Company from open cast mines at Phalaborwa, Transvaal, South Africa.

    In order to address concern on Health and Safety issues in the world-wide market for vermiculite, Palabora Europe have previously commissioned LOM Consulting to undertake a detailed analysis of vermiculite from the main PP & V ore body at Phalaborwa and one grade from the adjacent VODT deposit. This original study produced favourable results and has been followed up by routine screening of stocks.

    The main aims were to collect representative samples from each grade of vermiculite as available in the European market, split them and analyse them at the IOM Consultingís Edinburgh headquarters for asbestiform mineral and crystalline silica.


    Mr Steve Klek of IOM Consulting and Mr Mike Darling of Palabora Europe Limited visited the Palabora Europe Ltd vermiculite bulk store at North Killingholme Humberside, on 2nd December 2003. At the North illingholme site, there are normally six different grades of vermiculite stored inside large silos of approximately 27 metres diameter and 9 metres high (micron PP & V, superfine PP & V, fine PP & V, medium PP & V, large PP & V and superfine VODT). At the time of this exercise there were only five types in stock, there being no Superfine VODT.

    Samples were collected from each grade as representatively as possible, by clearing away loose dust from the top of the material and digging into the stock as far as possible, avoiding any material falling in and re-mixing. A number of sub samples per site were extracted and mixed from each stockpile. Each sample was split on site with one sample being retained by Palabora Europe and the rest by IOM Consulting.


    3.1 Asbestos

    The main objective was to identify any hazardous asbestos fibres present in the vermiculite. This was achieved as follows:

    1. Initial examination by stereo-binocular microscopy and polarised light microscopy using methods described in HSE document MDHS 77 (HSE, 1994a).

      A portion of each sample was examined for the presence of fibrous asbestos minerals at X8 - X40 magnification, using stereo-binocular microscopy. Any fibres detected, were mounted in appropriate refractive liquid and identified at 125X magnification using Polarised Light Microscopy (PLM) and dispersion staining microscopy. This part of this analysis was carried out under IOMís external quality accreditation, awarded by the United Kingdom Accreditation Service (UKAS).

    2. Quantitative assessment of amphibole asbestos by electron microscopy and X-ray diffractometry would normally then be carried out for samples in which asbestos fibres were detected in (i) above. In this instance, this was not done as there were no fibres identified.

    3.2 Crystalline silica

    A portion of each sample was ground up and analysed using X-ray diffraction techniques using modified versions of MDHS 51/2 (HSE 1988) and MDHS 76 (HSE 1994). Additional preparation of the Superfine PP&V sample was done to achieve a lower detection limit. Detailed method description is shown in the certificate of analysis in Appendix 1.


    4.1 Polarised Light Microscopy examinations did not detect any amphibole or chrysotile asbestos fibres present in any of the samples of vermiculite. As there were no amphibole or chrysotile asbestos fibres detected in any of the samples of vermiculite collected, quantitative analysis of the vermiculite materials was not undertaken.

    4.2. X-ray diffractometry did not detect any crystalline silica in any of the samples of vermiculite.

    4.3 A summary of results is given in Table 1. Certificates of Analysis are attached ( Appendix 1 and complete IOM report (.pdf format).

    Table 1. Summary of Results

    IOM Sample No.DescriptionAsbestosChystalline silia
    R763Medium (PP & V) None Detected None Detected *
    R764Micron (PP & V)None Detected None Detected*
    R765Fine (PP & V)None Detected None Detected*
    R766Large (PP & V)None Detected None Detected*
    R767Superfine (PP & V)None Detected None Detected*

    * The detection limit for quartz and cristobalite by this method is around 0.3%. This figure is based upon three times the standard deviation of the measurement of a blank sample run on a quantification programme. Previously, the detection limit was based upon the lowest amount, which could be detected on a qualitative programme, which was 0.1%. Although this has not changed, we are now required by the United Kingdom Accreditation Service (UKAS) to base our detection limit on the quantitative rather than the qualitative part of the analysis.


    5.1 The vermiculite materials tested comply with the proposed 0.1% European packaging and labelling of carcinogen requirements (HSE, 1994b) and the 0.1% trigger value for asbestos required for labelling of hazardous materials in the US.

    The levels are also lower than the 0.001% for asbestos in loose aggregates proposed by Addison et al (1988) based on work at the IOM using asbestos and soil mixtures. Therefore, it is concluded that these materials or products containing them should not present a significant asbestos-related health hazard when used in controlled occupational environment.

    5.2. Similarly with there being no crystalline silica detected in the samples and in consideration of the detection limits of the analysis, there should not be any health hazard, specifically related to crystalline silica, when the materials are used in a controlled environment.

    Considering an airborne total inhalable dust concentration of 10 mg/m≥, based on the higher limit of detection quoted in the certificate of analysis of <0.3%, the concentration of crystalline silica would be <0.03 mg/m≥; based on the lower limit of detection achieved for the Superfine PP&V sample, the airborne crystalline silica concentration would be 0.003 mg/m≥. This is in comparison with the current Maximum Exposure Limit of 0.3 mg/m≥ (8 hour TWA) given in HSE document EH40/2002.


    • Addison J, Davies LST. (1990). Analysis of amphibole asbestos in chrysotile and other minerals.
    • Ann.Occ.Hyg ; 34: 159-175.
    • Health and Safety Executive (1987). Quartz in Respirable Airborne Dusts. MDHS 37. HMSO London.
    • Health and Safety Executive (1998). Occupational Exposure Limits 1998. EH40/98. HSE Books, Sudbury.
    • Chung (1974). Quantitative Interpretation of X-ray Diffraction patterns of Mixtures. III Simultaneous Determination of a set of Reference Intensities. Sherwin-Williams Research Centre, Chicago, Illinois.
    • Health and Safety Executive (1988). Quartz in respirable airborne dusts. Laboratory method using x-ray diffraction (direct method). Methods for the Determination of Hazardous Substances No. 51/2. HMSO, London.
    • Health and Safety Executive (1994). Cristobalite in respirable airborne dusts. Laboratory method using X-ray diffraction (direct method). Methods for the Determination of Hazardous Substances No. 76. HMSO, London.

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