Glossary
Tone
Tone describes how light or dark a colour appears – from very light through medium to very dark. For ruby, sapphire and emerald, medium to medium-dark tones are usually the most sought after: the colour reads rich without turning dark. A stone that is too light looks pale; one that is too dark loses brilliance. Tone is always assessed together with hue and saturation.
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- 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
- 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
- GlossaryAbsorption spectrumWhen light passes through a gemstone, the stone absorbs certain wavelengths – the rest make up its colour.Read more
- GlossaryAfghanistanAfghanistan is an old source of ruby and emerald; both are mined in the mountains of the Hindu Kush.Read more
Updated 2026-10-06