[Jewelry making - Article 00224] - Re: [Orchid] Asbestos in Vermiculite

[Saabbe]

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    The following comes from the EPA's Information Page on Vermiculite.
    Asbestos Contamination In Vermiculite 

    http://www.epa.gov/

          Asbestos  contamination in vermiculite and vermiculite products
          has become a national  concern to a variety of federal agencies
          (EPA, OSHA, CPSC and ATSDR) and to many  private citizens
          throughout the country.  A tremendous amount of information has
          been made available to the public via print, television/radio 
          and the Internet.  EPA's vermiculite pages provides users with
          basic  information about Vermiculite and its uses, factsheets,
          Question and Answer documents, reports and links to EPA
          Regional vermiculite pages. Other relevant information, not
          included here, may be available from federal, state and local
          governments, industry, trade associations and international
          sources. Vermiculite and Its  Uses 

          What is  Vermiculite? 

          Vermiculite is the  mineralogical name given to hydrated
          laminar magnesium-aluminum-ironsilicate  which resembles mica
          in appearance. All vermiculite ores contain a range of  other
          minerals that were formed along with the vermiculite in the
          rock.  Vermiculite ores from some sources have been found to
          contain asbestos minerals  but asbestos is not intrinsic to
          vermiculite and only a few ore bodies have been  found to
          contain more than tiny trace  amounts. 

          Vermiculite mines are surface  operations where ore is
          separated from other minerals, and then screened or 
          classified into several basic particle sizes. Vermiculite is
          found in various  parts of the world. Locations of the
          predominant commercial mines are in  Australia, Brazil, China,
          Kenya, South Africa, USA and  Zimbabwe. 

          When subjected to heat,  vermiculite has the unusual property
          of exfoliating or expanding into worm-like  pieces (the name
          vermiculite is derived from the Latin 'vermiculare' - to breed
           worms). This characteristic of exfoliation, the basis for
          commercial use of the  mineral, is the result of the
          mechanical separation of the layers by the rapid  conversion
          of contained water to steam. The increase in bulk volume of 
          commercial grades is 8 to 12 times, but individual flakes may
          exfoliate as many  as 30 times. There is a color change during
          expansion that is dependent upon the  composition of the
          vermiculite and furnace temperature. 

          How Is Vermiculite Used? 

          Vermiculite has been used in  various industries for over 80
          years. It is used in the construction, agricultural,
          horticultural and industrial markets. Generic Applications -
          Loose Fill Carriers  Lightweight Aggregates Soil Conditioners
          Asbestos Substitutions Density Modifiers  Absorbents Fire
          Protection  Industrial Heat Insulation

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