Minerals important in asbestos analysis included in this family are chrysotile, lizardite, antigorite. Serpentine: A mineral family consisting of minerals with the general composition Mg 3(Si2O 5(OH) 4 having the magnesium in brucite layer over a silicate layer. Sealing Encapsulant: This is a product which can be applied, preferably by spraying, onto an asbestos surface which will seal the surface so that fibers cannot be released. Phase-Polar Microscope: The phase-polar microscope is a phase contrast microscope which has an analyzer, a polarizer, a first order red plate and a rotating phase condenser all in place so that the polarized light image is enhanced by phase contrast. Although fibers finer than 1 µm are visible, analysis of these is inferred from analysis of larger bundles that are usually present. It is used to see the same size fibers that are visible in air filter analysis. Phase-Polar Analysis: This is the use of polarized light in a phase contrast microscope. The technique which uses this is called Phase Contrast Microscopy (PCM). Phase Contrast Microscope: A microscope configured with a phase mask pair to create phase contrast. Phase Contrast: Contrast obtained in the microscope by causing light scattered by small particles to destructively interfere with unscattered light, thereby enhancing the visibility of very small particles and particles with very low intrinsic contrast. This is usually accomplished with a McCrone objective or other arrangement which places a circular stop with apparent aperture equal to the objective aperture in the back focal plane of the microscope.Ĭleavage Fragments: Mineral particles formed by the comminution of minerals, especially those characterized by relatively parallel sides and moderate aspect ratio.ĭifferential Counting: The term applied to the practice of excluding certain kinds of fibers from a phase contrast asbestos count because they are not asbestos.įiber: A particle longer than or equal to 5 µm with a length to width ratio greater than or equal to 3:1. 3:1.īrucite: A sheet mineral with the composition Mg(OH) 2.Ĭentral Stop Dispersion Staining (microscope): This is a dark field microscope technique that images particles using only light refracted by the particle, excluding light that travels through the particle unrefracted. (See section 3.5.)Īspect Ratio: The ratio of the length of a fiber to its diameter usually defined as “length : width”, e.g. Nominal compositions are listed:Ĭummingtonite-Grunerite asbestos (Amosite)Īsbestos Fiber: A fiber of asbestos meeting the criteria for a fiber. The precise chemical formulation of each species varies with the location from which it was mined. Asbestos includes chrysotile, cummingtonite-grunerite asbestos (amosite), anthophyllite asbestos, tremolite asbestos, crocidolite, actinolite asbestos and any of these minerals which have been chemically treated or altered. Minerals important in asbestos analysis include cummingtonite-grunerite, crocidolite, tremolite-actinolite and anthophyllite.Īsbestos: A term for naturally occurring fibrous minerals. The shape of each unit is similar to an “I beam”. Some terms unique to asbestos analysis are defined below:Īmphibole: A family of minerals whose crystals are formed by long, thin units which have two thin ribbons of double chain silicate with a brucite ribbon in between. This method describes the collection and analysis of asbestos bulk materials by light microscopy techniques including phase- polar illumination and central-stop dispersion microscopy. Similar products from other sources may be substituted. Appendix J to § 1910.1001 - Polarized Light Microscopy of Asbestos - Non-MandatoryĬollect approximately 1 to 2 grams of each type of material and place into separate 20 mL scintillation vials.Ī portion of each separate phase is analyzed by gross examination, phase-polar examination, and central stop dispersion microscopy.Ĭommercial manufacturers and products mentioned in this method are for descriptive use only and do not constitute endorsements by USDOL-OSHA.
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