• Webster's Revised Unabridged Dictionary
    • n Tetartohedrism (Crystallog) The property of being tetartohedral.
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Century Dictionary and Cyclopedia
    • n tetartohedrism In crystallography, the state or property of being modified tetartohedrally, or of being characterized by the presence of one fourth of the planes required by holohedral symmetry. It can most simply be regarded as resulting from the application of the two methods of hemihedrism, and hence is possible in the isometric, tetragonal, and hexagonal systems, in which the two kinds of hemihedrism are observed. Practically it has been noted in a few substances crystallizing in the isometric system, and in a number belonging to the hexagonal system. In the latter there are two kinds: the first is called rhombohedral tetartohedrism, when the resulting tetartohedral form is a rhombohedron, as, for example, with dioptase and phenacite; and the second trapezohedral tetartohedrism, when the resulting form is a trigonal trapezohedron: this is characteristic of quartz and cinnabar, and is important as being connected with the phenomena of circular polarization.
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In literature:

These systems, however, only represented holohedral forms, leaving the hemihedral and tetartohedral classes to be explained.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7" by Various