Mineralogy

1981 Edition

Allotropy

  • Rhodes W. Fairbridge
Reference work entry
DOI: https://doi.org/10.1007/0-387-30720-6_3

Allotropy (so named by J. J. Berzelius in 1841) refers to the existence of a chemical element in two or more distinct forms having different crystalline structures and/or physical properties. Allotropes may differ with respect to density, melting point, molar volume, color, and other physical properties. In some cases, there is a reversible, in others an irreversible transition from one allotrope to another.

Examples of Allotropy include:
  • carbon: chaoite , graphite , and lonsdaleite (hexagonal); diamond (isometric).

  • sulfur : native or α-sulfur (orthorhombic); γ-sulfur or rosickyite (monoclinic).

  • phosphorus: white/yellow (two forms: cubic and orthorhombic), violet and black (thus, four allotropes of contrasting properties); red phosphorus is a mixture.

  • tin : white (tetrahedral); gray (cubic).

  • iron: α-iron or kamacite (body-centered cubic and magnetic); γ-iron or taenite (face-centered cubic and nonmagnetic); δ-iron or ferrite (body-centered cubic and stable only above 1400°C).

  • oxygen...

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Reference

  1. Weaver, E. C., 1966. Allotropes, in G. L. Clark, ed., Encyclopedia of Chemistry, 2nd ed. New York: Reinhold.Google Scholar

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Copyright information

© Hutchinson Ross Publishing Company 1981

Authors and Affiliations

  • Rhodes W. Fairbridge

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