tetrahedral symmetry

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tetrahedral symmetry

[′te·trə¦hē·drəl ′sim·ə·trē]
(physics)
Having the same rotation symmetries as a regular tetrahedron.
References in periodicals archive ?
4 a, c, d) were generally stacked more loosely than pyritohedral (Fig.
In Vein 53 at Ait Ahmane (rich in quartz crystals and fibrous amphiboles), gray, thick-tabular clinosafflorite crystals are associated with octahedral and pyritohedral crystals of nickel-skutterudite.
Nickel-skutterudite also occurs in Vein 53, as lustrous pyritohedral and octahedral crystals with clinosafflorite.
Pyrite forms millimeter-size cubes with pyritohedral modifications and striations.
In the antimony mineralization, pyrite forms small 0.5 to 1-mm cubic or pyritohedral crystals and anhedral grains in quartz, carbonates and sulfide minerals (Cambel, 1959).
Pyritohedral crystals from marker 422.5, 990 level, however, reach 1.5 cm; some are coated with sooty chalcocite.
Pyrite cubes modified by the octahedron are predominant, though octahedral and pyritohedral forms may be found.
Pyrite is a minor association, occurring as striated, pyritohedral crystals less than 1 cm in size.
In addition, there also appeared bournonite on bright pyritohedral pyrite crystals, commonly about the same size as the bournonite, and these were typical of bournonite-pyrite assemblages from this particular batch; again, the bournonite crystals in the best specimens measure about 3 cm.
Colorless fluorite, pyritohedral pyrite, and arsenopyrite may occur with the enargite.
The cubes are often slightly modified by pyritohedral and octahedral forms that add extra, albeit small, faces to the edges and corners.
Pyrite is abundant both in cubic and pyritohedral habits.