trapezohedron


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trapezohedron

[trə¦pē·zō¦hē·drən]
(crystallography)
An isometric crystal form of 24 faces, each face of which is an irregular four-sided figure. Also known as icositetrahedron; leucitohedron; tetragonal trisoctahedron.
References in periodicals archive ?
Finally, in a manner similar to Curwen's portrait, Pickman's canvases, the Shining Trapezohedron, the queer Innsmouth jewelry, the statuette of Cthulhu, and Zann's music, ekphrasis in "Picture" reveals that art serves as a vehicle for the exploration of the human psyche's inner depths.
The positions of trapezohedrons, bipyramids and twinning patterns in the form of damascence (visible laminations) on gwindels betray the presence of Dauphine twinning.
When trigonal trapezohedron faces (x) are present on a gwindel they typically benefit from the twist, as the x faces on the stacked component crystals are brought into planar alignment with each other and merge into one enlarged face.
121), (211), (112), (112), (211), (121), (211), (112), (112), (121), (121) and (211)] and light symbols indicate faces of the trapezohedron that do not occur on the garnet [i.
The shapes of the belly bands (shaded) for the dodecahedron, the {211} trapezohedron, and the {321} hexoctahedron are given in Figure 19, along with the shapes of the (extended) belly band faces in their twins on [111].
The belly band of the {211} trapezohedron then corresponds to a hexagonal prism, but one that is rotated 60[degrees] with respect to the prism of the dodecahedron; i.
Thus, we find that the isometric forms which can produce twins with belly bands composed of pairs of coplanar faces, one from each half of the twin, are limited to the dodecahedron, the {211} trapezohedron, and those hexoctahedra for which h = k + l.
Are there elongated twins of the {211} trapezohedron or the permitted hexoctahedra?
Examples of first-rate Scottish zeolites in the two cases included very large specimens of basalt plates and open tubes lined with lustrous white stilbite "bowties" to 5 cm, thick coverages of lustrous white and colorless chabazite rhombs to 3 cm on matrix, perfect glassy analcime trapezohedrons to 2.
In their InnSuites room, Steve Behling and Sandor Fuss of Collector's Edge had laid out about 10 flats of matrix-plate specimens measuring from around 4 x 4 to 20 x 20 cm, with thick coverages of brilliant cinnamon-colored spessartine trapezohedrons, often with smoky quartz crystals to 4 cm, chalky white feldspar crystals to 1 cm, and tiny-but-sharp greenish hexagonal books of clinochlore, all these over a gray-white pegmatitic rock.
Further, Gilles had some new analcime specimens of a lovely, bluish white color, in lustrous trapezohedrons to 1 cm in groups up to 10 cm; in some miniatures, these "blue" analcimes come with clusters of bright yellow-brown curved siderite rhombohedrons averaging 5 mm.
Pollucite, a rare zeolite in a series with analcime, and crystallizing likewise in trapezohedrons, has popped up in soccer-ball-sized Pakistani crystals at shows before, strictly in a one-of-a-kind way.