zircon \zir"con\, n. f., the same word as jargon. see jargon
   a variety of zircon.
   1. min. a mineral consisting predominantly of zirconium
      silicate zr2sio4 occurring in tetragonal crystals,
      usually of a brown or gray color. it consists of silica
      and zirconia. a red variety, used as a gem, is called
      hyacinth. colorless, pale-yellow or smoky-brown
      varieties from ceylon are called jargon.
      1913 webster +pjc

   2. an imitation gemstone made of cubic zirconia.
      pjc

   zircon syenite, a coarse-grained syenite containing zircon
      crystals and often also elaeolite. it is largely developed
      in southern norway.
      1913 webster
see also:
jargon zr2sio4 hyacinth jargon cubic zirconia zircon syenite