Knowledge
What treatment disclosure means
Many gemstones are treated to improve colour or clarity. What matters is not whether a stone was treated but whether this is stated openly and precisely.
Treatments have been part of the gemstone trade for centuries. Rubies and sapphires are heated, emeralds filled with oil or resin, some stones irradiated. A treatment is not a moral judgement – but it affects rarity, value and care. That is why it must be disclosed.
What counts as a treatment
A treatment is any intervention beyond cutting and polishing that alters appearance, colour, clarity or durability. International nomenclature rules, such as those of CIBJO, require such interventions to be disclosed at the point of sale.
Common treatments
- Heating: improves colour and clarity, especially in corundum; often stable and permanent
- Filling fractures with oil, resin or glass: improves clarity, may change over time
- Irradiation and annealing: alter colour, for example in topaz or coloured diamonds
- Diffusion: introduces colouring elements into the stone from outside
- Coating: a thin surface layer, sensitive to wear
How a laboratory writes about it
A laboratory report describes which treatment was detected and often to what extent. For emerald, grades such as "none", "minor", "moderate" or "significant" are common. The exact wording matters: "no indications of heating" is a different statement from "untreated". Not every treatment can be detected with certainty; some reports state this explicitly.
Why it matters to you
An untreated stone of comparable quality is usually rarer. Fillings can be damaged by ultrasonic cleaning, heat or solvents. Knowing the treatment allows you to assess the stone correctly and care for it properly.
In brief
A treatment is neither good nor bad, but it must be stated openly and precisely. Read the laboratory's wording in full, including any qualifications. It determines how rare a stone is, how it is valued and how it must be cared for.
At NOBILITH
The dossier quotes the laboratory's treatment statement verbatim. We do not shorten it, and we do not infer a stronger statement from a missing one. Care guidance follows the treatment detected.
Sources
- CIBJO: The Gemstone Book, section on treatments
- LMHC: Information Sheets on standardised wording
- GIA: Gem Encyclopedia, treatments
Read more
- Laboratory reportsUnderstanding a laboratory reportA laboratory report is a gemstone's most important document. Which information it contains, how to read it and what it does not say.Read more
- Gem LabGemmological microscopeThe most important instrument in the laboratory: under the microscope, inclusions, growth features and signs of treatment become visible.Read more
- KnowledgeHow to read a gemstone dossierA dossier brings together everything that describes a stone – from the laboratory report to custody. Here is how to read it in the right order.Read more
- KnowledgeNatural, synthetic and imitation materialThree terms that are often confused: what they mean, how a laboratory tells them apart and why the classification must never rest on assumption.Read more
Updated 2026-10-06