(a) Gemstones may have been treated by heating (generally), or diffusion (sapphires) to enhance the colour of the stone.
(b) Created gemstones are grown in strictly controlled laboratory conditions to recreate the brilliance of rare natural gemstones.
(c) Black diamonds are enhanced by high temperature to permanently create the intense black colour.
(d) Blue, yellow and red coloured diamonds have been irradiated to achieve their colour. Colour treatments used on diamonds may be sensitive to high temperatures and heat.
(e) Enhanced blue turquoise stones are treated with a dye to enhance the natural blue colour.
