As treatment methods for colored gemstones continue to evolve, some enhancements
remain difficult or currently impossible to detect with certainty using available
gemological techniques.
To promote transparency and informed decision-making, GSI provides a reference table
highlighting gemstone types and treatments that may present detection challenges.
This information is intended to support responsible sourcing and raise awareness
within the trade.
As analytical capabilities advance, this information will be updated accordingly.
1. Amethyst Quartz
Commonly treated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
2. Aquamarine Beryl
Commonly heated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
3. Citrine Quartz
Commonly treated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
4. Demantoid Garnet
Not commonly treated. The presence or absence of heat treatment cannot currently be determined.
5. Heliodor Beryl
Commonly treated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
6. Kunzite Spodumene
Commonly treated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
7. Maxixe Beryl & Maxixe-type Beryl
Both owe their blue color to irradiation. Whether the treatment occurred naturally
in the earth (Maxixe) or was artificially induced by man (Maxixe-type) cannot
currently be determined. The color in both is unstable and may fade with prolonged
exposure to light or heat.
8. Morganite Beryl
Commonly heated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
9. Paraiba-type Tourmaline
Commonly heated to improve or modify color. The presence or absence of such treatment cannot always be determined.
10. Rubellite Tourmaline
Commonly treated to improve color. The presence or absence of such treatment cannot currently be determined.
11. Rubellite Tourmaline (Irradiated)
May be irradiated to improve color. The presence or absence of such treatment cannot currently be determined.
12. Smoky Quartz
Commonly treated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
13. Tanzanite Zoisite
Commonly heated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
14. Tiger's-Eye Quartz
May be heated or bleached to improve or modify color. The presence or absence of such treatment cannot currently be determined.
15. Topaz
May be treated to improve or modify color. The presence or absence of such treatment cannot currently be determined.
16. Tourmaline
May be treated to improve or modify color. The presence or absence of such treatment cannot currently be determined.