disphenoid


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disphenoid

[dī′sfē‚nȯid]
(crystallography)
A crystal form with four similar triangular faces combined in a wedge shape; can be tetragonal or orthorhombic.
A crystal form with eight scalene triangles combined in pairs.
References in periodicals archive ?
The crystal form is the tetragonal disphenoid ("pseudotetrahedron") (Figs.
bicupola puboiliac (W2) bigyrate betraying (W3) birotunda obdurating (W3) dipyramid pyramidoid (OED) disphenoid hypnoidised (W2 has the -ize infinitive form) elongated delegation (W3) gyrate tragedy (W3) pyramid myriapod (W3) rotunda untoward (W3) triangular granularity (W3) Footnote:Pictures of all the Johnson solids are onlineatmathworld.wolfram.com/JohnsonSolid.html.
The habit is a simple disphenoid, although some crystals appear to be etched or to have unusual modifications.
Small disphenoids may be skewered by several millerite crystals.
The disphenoid is {112}, which is the usually dominant form on chalcopyrite crystals (Palache et al., 1944).
Most crystals form simple disphenoids 2-5 mm across scattered on the surfaces of calcite crystals or included within them.
Rarely chalcopyrite also occurs in small cavities in the siderite ore as well-formed disphenoids 1-3 mm across.
It is found as bright yellow tetragonal disphenoids and twinned crystals up to 6 cm in size, associated with pyrrhotite, galena and sphalerite at the First Sovietskiy, Second Sovietskiy, Sentyabr'skiy and Nikolaevskiy mines as well as the Bor pit.
Chalcopyrite usually occurs as disphenoids, giving the crystals a pseudo-tetrahedral crystal shape.
Single disphenoids over 9 cm on an edge have been found there.
Stope 45-13-0 produced lustrous disphenoids ([less than] 1 mm) intimately associated with sphalerite on gemmy clear quartz crystals.