The Passion of
Bleaching – a chemical used to alter/reduce a
component of, or the entire color of, a porous gem.
Some gemstones are bleached and then dyed, most
notably done to jadeite and pearl.
Dyeing – introducing colored dyes into porous or
fractured gems to change their color. Such fractures
are sometimes purposely induced by heating and
quench crackling the gem so that an otherwise nonporous
material can more readily accept the dye.
Fracture or Cavity Filling – filling surface-reaching
fractures or cavities with a glass, resin, wax or
oil to reduce their visibility and to improve the
apparent clarity or durability of gem materials. The
filling materials vary from being solids (a glass) to
liquids (oils), and in most cases, they are colorless
(colored filler materials could be classified as
dyes), most notably done to emeralds.
Heat Treatment – the exposure of a gem to various
elevated temperatures for the purpose of altering its
color and/or clarity, or improving its durability. It is
potentially done to many gems but most notably to
rubies and sapphires.
Left, rough and polished untreated zoisite.
Right, rough and polished heat-treated tanzanite.
Impregnation – the surface of a porous gemstone
is permeated with a polymer, wax or plastic to give
it greater durability and improve its appearance.
This treatment is most notably done to jadeite
Irradiation – exposure of a gem to an artificial
source of radiation to change its color. This is
sometimes followed by a heat treatment to further
modify the color, most notably done to blue topaz.
Left, natural topaz rough.
Right, irradiated polished blue topaz.
Lattice Diffusion – the penetration of certain
elements into the atomic lattice of a gemstone
during heat treatment, with the objective of
changing its color, most notably done to sapphire.
Lattice diffusion changed this
pink sapphire to orange
While many gemstone treatments can improve
color and clarity, some are not stable and may
reduce the value of a stone significantly. Always get
a GIA Colored Stone Report to ensure you know the
quality of your stone and if it has undergone any