Ogdohedry

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Ogdoédrie (Fr). Ogdoedrie (Ge). Ogdoedria (It). 八面像(Ja). Ogdoedría (Sp).


Definition

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 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 the case of rhombohedral crystals, it corresponds instead to a tetartohedry).

See also