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Isomorphism identification and geology

The phenomenon in which two or more minerals have the same crystal structure but different chemical compositions, with ions of similar size and charge substituting for one another in the lattice. Isomorphous minerals form solid solution series—such as the olivine series between forsterite Mg₂SiO₄ and fayalite Fe₂SiO₄ —in which properties vary continuously with composition. Field: mineralogy. Example: The plagioclase feldspar series from albite NaAlSi₃O₈ to anorthite CaAl₂Si₂O₈ is a classic example of isomorphism, with sodium and silicon continuously substituting for calcium and aluminum across the compositional range.. Related terms: Solid solution, Polymorphism, Substitution, Crystal structure.

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  • Polymorphism

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.127987+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Isomorphism mean in geology?
The phenomenon in which two or more minerals have the same crystal structure but different chemical compositions, with ions of similar size and charge substituting for one another in the lattice. Isomorphous minerals form solid solution series—such as the olivine series between forsterite Mg₂SiO₄ and fayalite Fe₂SiO₄ —in which properties vary continuously with composition.
What is an example of Isomorphism?
The plagioclase feldspar series from albite NaAlSi₃O₈ to anorthite CaAl₂Si₂O₈ is a classic example of isomorphism, with sodium and silicon continuously substituting for calcium and aluminum across the compositional range.
Which earth-science field uses the term Isomorphism?
Isomorphism is used in mineralogy.
Which terms are related to Isomorphism?
Related terms in this reference are Solid solution, Polymorphism, Substitution, Crystal structure.

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