Jargoon or jargon (occasionally in old writings jargounce and jacounce) is a name applied by gemologists to zircons that are of sufficient quality to be cut as gemstones, but not the red color that characterizes the hyacinth or jacinth. The word is related to Persian zargun (zircon; zar-gun, "gold-like" or "as gold").
Some of the finest jargoons are green, others brown and yellow, while some are colorless. The colorless jargoon may be obtained by heating certain colored stones. When zircon is heated it sometimes changes color, or loses it, and at the same time usually increases in density and brilliancy. The so-called Matura diamonds, formerly sent from Matara (or Matura) in Sri Lanka, were decolorized zircons.