GEMSTONE TREATMENTS

Andamooka Opal: Is treated by the Sugar-Acid method, which introduces sugar a ways into the slightly porous stone, and then darkens it, so that light reflecting off the matrix will distract less from the POC in the gem, (pushing the base towards Black Opal).

Aquamarine: Traditionly a sea blue-green, today it's usually heated [H], which drives off a yellow component, leaving the more popular, bluer shades.

Citrine: I'm told that most Citrine is heated [H], either to improve its color, or to actually change the more abundant Amethyst into Citrine, but my dealers always assert their citrine is natural, and unheated. Both may be true, considering I shop in alternative channels. When I'm convinced of one or the other I mark the gems individually. In specimin grades I can tell them apart, and don't like the heated ones.

Sapphire and Ruby: Almost always Heated [H], improving clarity and color.
Diffusion [D] is heated in the presence of other minerals, which share some molecules and color. Diffusion is often used to give Stars a more uniform blue appearance, and recently yellow to orange [BeD] have become popular additions, which is good in that I couldn't get the matching intense colors previously. The range of colors added is growing, and Thai dealers are often among the last to admit their stones are treated, so I sometimes have to speculate on probable treatments based on my experience.

Topaz: Almost all Blue Topaz has been Irradiated [Ir], and may still be slightly radioactive. [a suggestion has been made to consider not wearing large, dark (London) Blue Topazes over your heart as a daily habit] Some Pink Topazes have been heated, but they're real hard to find, anyway. Topaz does naturally come in a rainbow of colors, sometimes in a single crystal, but white (often treatable to blue), is the most common by far.

Turquoise: Often given a resin backing for strength. Most Turquoise today, (although little of mine), is treated with a resin to close its pores, and improve its strength, sometimes color can be added at the same time [I avoid these, as they don't look right].