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Vermiculite mineral


A laminar micaceous mineral composed of hydrated magnesium aluminum iron silicate. Vermiculite occurs naturally as a compact ore. It is mined in Russia, Australia, Brazil, South Africa, and the U.S. (Montana, North Carolina, South Carolina, Wyoming, Colorado). When vermiculite is heated to about 300 C (570 F), it expands to form highly porous, worm-shaped curls of connected mica-like plates. Expanded vermiculite is used as a fire-resistant insulator, spill absorbent, and packing material. It is also used as a lightweight filler in Plaster, Concrete, Brick, Rubber, Soil, Paper, Paint, and plastics.

Vermiculite, expanded

Synonyms and Related Terms

hydrated magnesium aluminum iron silicate; exfoliated hydrobiotite; Zonolite insulation; Microfil; Microlite; Verxite




Vermiculite mined prior to 1990 may contain asbestos which is toxic by ingestion and inhalation.

Noncombustible. Resistant to insects, bacteria, and fungi.

Milllipore Sigma: SDS

Other Properties

Unaffected by water, acids, alkalis or organic solvents.

Can expand 6-20 times when heated. Expanded vermiculite can absorb 200-500% of its weight in liquid.

Fracture = unvevn Crystal system = monoclinic Cleavage = perfect Streak = pale yellow

CAS 1318-00-9
Mohs Hardness 2-3
Density 0.04-0.15 (expanded)

Resources and Citations

  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 10095
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
  • Ceramics and Glass Conservation Section, List of Workshop Materials, The British Museum, London.