BIPYRAMIDAL  CLASS (Parallel-faced hemihedral) . The elements of symmetry are a tetrad See also:

• AXIS (Lat. for " axle ")

axis with a See also:

• PLANE

plane perpendicular to it, and a centre of symmetry . The See also:

• SIMPLE

simple forms are the same here as in the See also:

• HOLOSYMMETRIC

holosymmetric class, except the See also:

• PRISM (Gr. rrpivµa, properly a thing sawn, Irpii"ety, to saw)

prism {hko}, which has only four faces, and the bipyramid {hkll, which has eight faces and is distinguished as a " tetragonal See also:

• PYRAMID

pyramid of the third 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

order." See also:

• COMBINATION (Lat. combinare, to combine)

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 See also:

• FIGS

figs . 87 and 88 . Examplesof substances which crystallize in thisclass are cassiterite, See also:

• RUTILE

rutile, See also:

• ANATASE

anatase, See also:

• ZIRCON

zircon, See also:

• THORITE

thorite, See also:

• VESUVIANITE

vesuvianite, See also:

• APOPHYLLITE

apophyllite, See also:

• PHOSGENITE

phosgenite, also See also:

• BORON (symbol B, atomic weight I I)

boron, See also:

• TIN (Lat.- stannum, whence the chemical symbol " Sn "; atomic weight =117.6, 0=16)

tin, mercuric iodide .