Knowledge
Why a laboratory may say inconclusive
Sometimes a question cannot be answered responsibly with the available data. What “inconclusive” means – and what it does not.
A laboratory report marked "inconclusive" or "undeterminable" looks at first like a shortcoming. In fact it is a sign of professional care: the laboratory only states what it can support.
What the wording means
"Inconclusive" means the data collected do not allow a conclusion the laboratory can stand behind. The question remains open. It is not a hidden negative statement and not an indication of forgery.
Where it often occurs
- Origin: stones from different deposits can have very similar features, for example sapphires from certain basalt-related deposits or emeralds with few characteristic inclusions.
- Treatment: some low-temperature heating leaves hardly any traces.
- Cause of colour: in coloured diamonds it is not always clear whether the colour is natural or altered by treatment; the report is then withheld or worded accordingly.
Why the laboratory does not simply estimate
A laboratory report is used as a basis by buyers, insurers and auction houses. An estimate presented with the appearance of certainty would abuse that trust. International laboratory standards, such as the recommendations of the Laboratory Manual Harmonisation Committee (LMHC), therefore explicitly provide for uncertainty to be stated.
What you can do
- obtain a report from a second recognised laboratory with different reference data
- ask which examinations were carried out
- judge the stone on what is documented, not on what remains open
Effect on value
A stone without a determinable origin is generally not traded with the premium that a sought-after origin commands. Its other qualities are unaffected.
In brief
“Inconclusive” means the data do not allow a responsible conclusion. It is a sign of professional care, not a hidden negative verdict. Judge the stone on what is documented and, for important questions, consult a second recognised laboratory.
At NOBILITH
If a report says "inconclusive", the dossier states exactly that. We replace the open question neither with an assumption nor with an origin taken from the purchase records. Missing certainty is clearly shown as such.
Sources
- LMHC: Information Sheets and standardised wording
- SSEF and Gübelin: explanatory notes on their reports
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