From Online Dictionary of Crystallography

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Ogdoédrie (Fr). Ogdoedria (Sp). Ogdoedria (It)


The point group of a crystal is called ogdohedry if it is a subgroup of index 8 of the point group of its lattice.

In the three dimensional space there is only one ogdohedry: it corresponds to the geometric crystal class 3 of crystals belonging to the hexagonal lattice system (in case rhombohedral crystals, it corresponds instead to a tetartohedry).

See also

Section 9.1 of International Tables of Crystallography, Volume A