Transparency & disclosure

Gemstone Treatments & Disclosure

Many gemstones in the international market are treated to improve colour, clarity, durability, or overall appearance. A treatment is any process beyond standard cutting and polishing intended to enhance a gemstone's appearance or performance.

A treated gemstone is not automatically inferior. Many traditional treatments are stable, widely accepted, and have been part of the gem trade for generations. What matters is that any treatment is described correctly, the buyer understands its nature, and any relevant care considerations are clearly stated.

Our disclosure philosophy

We aim to describe every gemstone as clearly and honestly as possible. When a gemstone is untreated, heated, oiled, filled, dyed, coated, irradiated, diffused, or otherwise enhanced, this is stated in the product information. If no external laboratory report is included, our descriptions are based on the known history of the rough or stone, supplier information, our own gemological experience, and available examination methods. Where a treatment cannot be conclusively determined, we use wording such as "Treatment Not Determinable" rather than making unsupported claims.

Common treatments

No heat No Heat

No indication of heat treatment has been detected. Used primarily for ruby and sapphire, where heat treatment is the key market-relevant question. Unless another treatment is stated, "No Heat" generally indicates an untreated ruby or sapphire.

Untreated Untreated

No indication of artificial enhancement beyond standard cutting and polishing. Mainly used for gemstone varieties where heat treatment is not the usual primary treatment category.

Heat Traditional Heat

A long-established heat treatment used primarily to improve or stabilise colour and/or clarity. Widely accepted in the gemstone trade, stable, and does not require special care.

Heat + flux Heated & Fissure Healing

Heat treatment with flux additives. Some fissures may be partially healed during the process, and flux residues may remain within the stone. Stable, no special care required.

Residue Level 1 — Minor: Minor flux residues within healed fissures or internal features.
Residue Level 2 — Moderate: Moderate flux residues within healed fissures or internal features.
Residue Level 3 — Significant: Significant flux residues within healed fissures or internal features.
Be diffusion Heat with Be / Light-Element Diffusion

High-temperature treatment with beryllium or other light elements that can diffuse deeply into the corundum crystal lattice, modifying colour throughout the stone. Generally stable, though recutting may affect colour appearance in some cases.

Surface diffusion Surface Diffusion

High-temperature treatment with colouring elements introduced from an external source. The induced colour is concentrated in a shallow layer at and below the surface.

Repolishing or recutting may partially or significantly remove the diffused colour.
Irradiated Irradiated

Exposed to controlled irradiation to change or improve colour, sometimes followed by heat treatment. Colour stability depends on the gemstone variety — some irradiated colours are stable, while others may fade with prolonged exposure to strong light or heat.

Oiled Oiled

Treated with colourless oil to reduce the visibility of surface-reaching fissures and improve apparent clarity. Common in emerald.

Oil Level 1 — Minor: Minor oil present in surface-reaching fissures.
Oil Level 2 — Moderate: Moderate oil present in surface-reaching fissures.
Oil Level 3 — Significant: Significant oil present in surface-reaching fissures.
Avoid ultrasonic cleaning, steam, strong heat, and harsh chemicals.
Fracture fill Fracture-Filled

Surface-reaching fissures or cavities filled with resin, polymer, or another foreign substance to improve apparent clarity and appearance.

Filling Level 1 — Minor: Minor filling in surface-reaching fissures or small cavities.
Filling Level 2 — Moderate: Moderate filling in surface-reaching fissures or cavities.
Filling Level 3 — Significant: Significant filling in fissures or cavities.
Avoid ultrasonic cleaning, steam, strong heat, solvents, or aggressive repair work.
Glass fill Glass-Filled

Fissures or cavities filled with glass, often lead glass, to improve appearance and apparent clarity. A significant treatment requiring special care.

Avoid heat, ultrasonic cleaning, steam, and harsh chemicals.
Dyed Dyed

Colouring agents introduced to alter, intensify, or improve colour uniformity.

May be sensitive to solvents, chemicals, heat, and prolonged exposure to strong light.
Coated Coated

A surface coating applied to alter or improve the gemstone's colour or visual effect.

May be sensitive to abrasion, polishing, heat, solvents, and ultrasonic cleaning.
Bleached Bleached

A chemical or light-based process used to lighten or remove unwanted colour. Sometimes combined with dyeing or impregnation and may require special care.

Impregnated Impregnated / Stabilised

A porous gemstone permeated with wax, resin, polymer, or another stabilising substance to improve durability, surface appearance, or colour.

Avoid heat, solvents, ultrasonic cleaning, and harsh chemicals.
Waxed Waxed

A colourless wax or similar substance applied to or near the surface to improve lustre or appearance.

Keep away from heat, solvents, and aggressive cleaning methods.
Assembled Assembled Stone / Doublet / Triplet

An assembled gemstone made from two or more joined parts. Not a single solid natural gemstone and should be handled with care.

Avoid heat, prolonged water exposure, ultrasonic cleaning, and solvents.
Undetermined Treatment Not Determinable

Current gemological science does not provide a reliable method to prove or exclude certain treatments in this case. The colour may be natural or may have been modified by treatment, but no conclusive laboratory determination is currently possible.

Care for treated gemstones

General cleaning

Lukewarm water, mild soap, and a soft brush. Store gemstones separately to prevent scratching.

Avoid for sensitive stones

No ultrasonic cleaning, steam, strong heat, solvents, acids, or harsh chemicals — especially for oiled, filled, dyed, coated, or impregnated stones.

Before jewellery work

Always inform your jeweller about any known treatment before resizing, polishing, cleaning, or repair work.

Laboratory reports For higher-value gemstones — especially ruby, sapphire, emerald, alexandrite, spinel, and other collector stones — independent laboratory reports provide additional confidence. When a report is included, the issuing laboratory and treatment conclusion are shown in the product information. Gem-Fountain can also arrange additional testing upon request.