BIPYRAMIDAL
This article appears in Volume V07, Page 577 of the Encyclopedia Britannica.
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Encyclopedia Britannica - Main :: BER-BLA
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BIPYRAMIDAL CLASS (Parallel-faced hemihedral). The elements of symmetry are a tetrad axis with a plane perpendicular to it, and a centre of symmetry. The simple forms are the same here as in the holosymmetric class, except the prism {hko}, which has only four faces, and the bipyramid {hkll, which has eight faces and is distinguished as a " tetragonal pyramid of the third order See Also: - ORDER
- ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
- ORDER, HOLY
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Combination of Tetragonal Prism and Basal Pinacoid.
combination of a bipyramid of the first order See Also: - ORDER
- ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
- ORDER, HOLY
with a ditetragonal bipyramid and the prism of the second order. Compare also figs . 87 and 88. Examplesof substances which crystallize in thisclass are cassiterite, rutile , anatase, zircon, thorite, vesuvianite, apophyllite, phosgenite, also boron , tin, mercuric iodide.
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