pyritohedron


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Related to pyritohedron: Scalenohedron, rhombohedron

pyritohedron

(ˌpaɪrɪtəʊˈhiːdrən)
n, pl -drons or -dra (-drə)
(Minerals) crystallog a twelve-sided polyhedron with pentagonal faces, common in crystals of pyrite
References in periodicals archive ?
9c-g, it could be observed that the cell of CEPBS has fine shape (pyritohedron), closed-cell, and uniform cell distribution, which should be attributed to the chain extension and cross-linking effects.
The Tweefontein Farm in South Africa produced sperrylite crystals up to 2.6 cm in the 1920s (see Wilson, this issue), but this size record was surpassed in the 1990s by sperrylite discovered at Norilsk in well-crystallized cubes modified by octahedron and pyritohedron faces that reach over 4 cm on edge.
The following forms were identified: the rhombic dodecahedron, the pyritohedron, the trapezohedron, several dyakis dodecahedra, and probably the triakis octahedron [= trisoctahedron], Wagner stated that the Tweefontein sperrylite crystals are typically 1.3 mm to 1.7 cm in size.
Sharper, smaller crystals as a rule show combinations of the pyritohedron, rhombic dodecahedron, cube and octahedron; cuboctahedrons are especially common whereas simple octahedrons are rare.
Bateman reports massive pyrite, and one specimen of a distorted pyritohedron, but a search of the Yale collection did not reveal the piece.
Of all the "common" things in the collection perhaps the most abundantly represented are sharp mahogany-brown pseudomorphs of goethite ("limonite") after pyrite cubes and pyritohedrons: John has specimens of these from perhaps a half-dozen localities, although the best are from Lancaster, Pennsylvania, where kids who dig these out of the soil call them "monkey gold" (I know, for I was once one of those kids).
From the Moon-lite claim, Bullion Canyon, Tooele County, groups of lustrous cubes and pyritohedrons, with individuals to 4 cm on edge, emerged during the 1980s and 1990s; from the Four Metals mine, also in Bullion Canyon, clusters of distorted pyrite cubes, individuals to 5 cm, on greenish clay matrix, emerged during the past few years.
These are groups of pyritohedrons, mirror bright, in miniature sizes--really superb.