Online Encyclopedia
Make a correction
Your email address will not appear on the site. Note, comments may take some time to be approved.
Back to article:
BIPYRAMIDAL
Your email:
Article name:
Article content:
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." Combination of Tetragonal Prism and Basal Pinacoid. combination of a bipyramid of the first order 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.