Treatments in gems
Gems can be treated to enhance their color or clarity. Discover which are the most common ones.
Lattice diffused sapphire (2022)Instituto Gemológico Español (IGE)
The passion for gems has caused the development of numerous treatments to improve their color or purity, allowing a broader offer in the market.
Dyed quartz (2023)Instituto Gemológico Español (IGE)
It is important to highlight that some of these treatments are stable, and some of them may vary their properties.
There are many techniques that allow their identification, either conventional as microscope or magnifying glass, or advanced such as spectroscopy, x-ray, etc.
Heat treated sapphire (2022)Instituto Gemológico Español (IGE)
1. Heat treatment
One of the most common ones is the heat-treatment with high temperatures, enhancing their color and clarity. It is quite common in corundum, tanzanite and zircon.
Lattice diffused sapphire (2023)Instituto Gemológico Español (IGE)
2. Lattice diffusion
This treatment is aimed to change or accentuate the color of a gemstone putting certain elements (titanium, beryl or chromium) into the atomic lattice during heat treatment.
Irradiated diamond (2021)Instituto Gemológico Español (IGE)
3. Irradiation
Exposing a gem to radiation, gamma ray for instance, may change its structure, producing different colours. Depending on the gem, this treatment may be stable or not; the colour may fade in some gemstones if they are exposed to bright light.
Non treated coral and impregnated coral (2024)Instituto Gemológico Español (IGE)
4. Impregnation
A polymer or wax is applied in the surface of porous gems such as jade, opal, coral or turquoise to improve its appearance and to give a greater durability.
Surface coated topaz (2022)Instituto Gemológico Español (IGE)
5. Surface coating
It is used to alter a gem’s appearance by applying a coloring agent in the surface. It is commonly used in quartz, cubic zirconia or topaz (“mystic topaz”).
Fracture filled emerald (2022)Instituto Gemológico Español (IGE)
6. Fracture or cavity filling
This treatment is aimed to enhance the transparency of a gem, filling fractures or cavities with colored or colorless vitreous or non-vitreous substances.
It is easy to detect it using a 405nm laser pointer, due to the different fluorescence of each material.
Fissure healed sapphire (2023)Instituto Gemológico Español (IGE)
7. Fissure healing
It is used to improve transparency in corumdum. In this case, fissures are filled with borax.
Dyed opal (2022)Instituto Gemológico Español (IGE)
8. Dyeing
It consists of the application of coloring substances into porous or fractured gems to improve their color (jades, agates, opals).
Fissure healed ruby (2023)Instituto Gemológico Español (IGE)
Other treatments
The development of new treatments forces gemologists to constantly update themselves to be able to detect them, since their presence or absence has an impact on the value of gems.
Photo credit: Ana de Bustos Ruiz, José Alonso, Joaquín Lorenzo, Irene Gobet
Written by: Irene Gobet. Text revision: Marta del Teso, Almudena Gómez
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