Ogdohedry

Ogdoédrie (Fr). Ogdoedria (Sp). Ogdoedria (It). 八面像 (Ja)

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 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 3.2.1 of International Tables of Crystallography, Volume A, 6^th edition