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LITHOEN

Mineral

Almandine

The iron–aluminium garnet, common in metamorphosed shales and a standard indicator of metamorphic conditions.

Five groups of triangles representing silicon-oxygen tetrahedra, arranged as isolated units, a single chain, a double chain, a sheet and a framework, each labelled with example minerals and a silicon-to-oxygen ratio.
SchematicHow silicon–oxygen tetrahedra link, and what each arrangement produces. Sharing more oxygens between tetrahedra lowers the oxygen content relative to silicon, from 1:4 in isolated tetrahedra to 1:2 in a framework — which is why the structural class can be read from the formula.
Full description of this figure

The diagram sets out five structural classes of silicate. Isolated tetrahedra share no oxygens and give Si:O of 1:4, as in olivine and garnet. Single chains share two oxygens per tetrahedron, giving 1:3, as in pyroxene. Double chains share two and three alternately, giving 4:11, as in amphibole. Sheets share three, giving 2:5, as in mica and clay. Frameworks share all four, giving 1:2, as in quartz and feldspar. Moving left to right is a progression of increasing polymerisation.

Original Lithoen diagram · LITHOEN-ORIGINAL

Classification

formula
Fe2+3Al2(SiO4)3
ima status
grandfathered
crystal system
cubic

How this record is known

1
Settled consensus
Cited as the accepted position of the discipline.

1 of 1 claims on this page cite at least one registered source. Counts describe how each statement is known, not how likely it is to be true.

What Lithoen records

Each claim states how it is known and cites its evidence.

EstablishedFe2+3Al2(SiO4)3

Almandine is an accepted mineral species in the IMA List of Minerals, with the CNMNC-approved formula Fe2+3Al2(SiO4)3 and IMA status “grandfathered”.

  • definition basis: IMA List of Minerals, September 2026 update, which is the authority on mineral species status.
  • precision note: An approved formula is an idealised composition; natural crystals of most species depart from it through substitution.

Evidence support: Supported by the cited evidence one source

Evidence: Commission on New Minerals, Nomenclature and Classification, International Mineralogical Association 2026 Primary authority

In the knowledge graph

  • Almandine member of Garnet
  • Almandine forms a solid solution with Pyrope
  • Almandine has essential constituent Aluminium
  • Almandine has essential constituent Iron
  • Almandine has essential constituent Oxygen
  • Almandine has essential constituent Silicon

Record last updated 2026-09-06. Corrections follow the published corrections policy; superseded claims are retained, never silently edited.