tetrahexahedron


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tetrahexahedron

[‚te·trə′hek·sə‚drän]
(crystallography)
A form of regular crystal system with four triangular isosceles faces on each side of a cube; there are altogether 24 congruent faces.
References in periodicals archive ?
The eight crystal drawings shown comprise the set of observed magnetite crystal habits, made up of varying degrees of the development of just three forms: the cube, the tetrahexahedron, and the octahedron.
Tetrahexahedron faces, although sometimes smooth, more often show a variety of very interesting microscopic textures that lead to striations and frosted surfaces when such specimens are viewed with the naked eye.
Additionally, the hexoctahedron and tetrahexahedron forms, while rare in most areas, are quite common at the Mex-Tex.
These are superb octahedrons nicely modified by truncated edges and low-angle tetrahexahedron faces.
Minor modifications include the tetrahexahedron on the (100) face or beveled crystal edges.
On some crystals the dodecahedrons are modified by narrow faces of the {1211} trapezohedron, sometimes in combination with small faces of the cube {100}, or a tetrahexahedron. This latter form has not been measured.
The habit of some of the gold is dendritic to arborescent; some arborescent groups have rounded gold tetrahexahedrons to 2 mm resting on the tips of the "branches." Other specimens are clusters of sharp, deeply hoppered gold octahedrons to 1 cm; others are dominated by wire gold; still others show sponge gold as "matrix" for crystal groups; a couple of exceptional pieces have distorted dodecahedral gold crystals to 2 cm resting on quartz.
The first occurs either as radiating aggregates composed of individual blades of fluorite, which form intergrown hemispheres typically no more than 7 mm across (or isolated hemispheres as much as 2.2 cm across), or as rough tetrahexahedrons as large as 1.5 cm.
Delicate, acicular crystals are occasionally seen in cavities within massive quartz, associated with small botryoidal to hemispherical fluorite aggregates or crude fluorite tetrahexahedrons.
The crystalized copper occurs as rough tetrahexahedrons (M.