Masterclasses
Alexandrite
A considered NOBILITH introduction to alexandrite: colour, character, documentation and individual selection.
At NOBILITH, alexandrite is introduced as a complete gemstone rather than a single visual impression. Alexandrite is the colour-change variety of chrysoberyl. Its ability to appear greenish in daylight and reddish or purplish under incandescent light is caused by selective absorption and is central to its identity.
Chapters
Introduction
At NOBILITH, alexandrite is introduced as a complete gemstone rather than a single visual impression. Alexandrite is the colour-change variety of chrysoberyl. Its ability to appear greenish in daylight and reddish or purplish under incandescent light is caused by selective absorption and is central to its identity.
Formation
Every alexandrite carries a history of formation, growth and change. Alexandrite forms in unusual geological environments where beryllium and chromium are available together. Natural material is rare, and laboratory examination is essential.
Mineralogy and chemistry
Its mineral identity provides the foundation, while the individual stone gives that foundation its character. Chrysoberyl is beryllium aluminium oxide. Chromium contributes to the colour-change effect, while the strength and quality of the effect vary with chemistry, lighting and cut.
Colour
Colour is often the first thing we notice, but it is the balance of the whole stone that holds the eye. Colour change is assessed under defined light sources and viewing conditions. Strength, completeness, body colour, tone and saturation should all be described rather than reduced to a simple yes-or-no claim.
Origins
Locality can add context to a gemstone, but it belongs to the evidence of the individual stone and not to assumption. Historic Russian material is important, while Sri Lanka, Brazil, East Africa and other sources are also known. Origin is a laboratory opinion and may be inconclusive.
Inclusions
The interior of a gemstone is part of its story and should be read with curiosity and restraint. Natural alexandrite may contain needles, crystals, fingerprints and growth features. Inclusions can support assessment but do not independently prove origin.
Gem Lab
Alexandrite microscope study
Compare internal features and the lighting conditions used when discussing alexandrite's colour change.
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Microscope images: illustrations of typical features, not a laboratory finding.
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Inclusions
Inclusions are examined as part of the identity and clarity description of alexandrite.
Treatments
Treatment belongs in the dossier because it shapes how a gemstone should be understood, cared for and described. Treatment status must be documented. A colour-change effect should not be assumed to indicate natural origin, untreated status or a particular locality.
Cut and proportions
Cut is where material becomes presence: it controls how the gemstone meets light and how it feels when viewed. Cut orientation can influence colour and colour change. Good cutting balances effect strength, transparency, brilliance, weight and durability.
Quality characteristics
A serious assessment looks for balance rather than a single headline characteristic. The strength and attractiveness of colour change, body colour, transparency, inclusions, cut, size and report quality all contribute.
Laboratory examination
Laboratory work is strongest when several observations are brought together and interpreted in context. Laboratories use microscopy, optical observation, spectroscopy and chemical analysis where appropriate. Lighting conditions and report terminology should be recorded precisely.
Origin determination
An origin opinion is valuable precisely because it is evidence-led and allowed to remain inconclusive when necessary. Origin requires combined evidence. A report that states an inconclusive origin is a valid professional result, not a defect.
Understanding the report
A report becomes useful when it is read as one part of the gemstone's wider identity and dossier. Verify material identity, colour-change description, treatment statement, origin opinion, photographs, measurements and report number.
History and significance
The cultural story of a gemstone can enrich ownership while remaining separate from its examination record. Alexandrite has become associated with transformation and rarity because of its changing appearance. Its most reliable story remains the evidence attached to the individual stone.
NOBILITH Selection
NOBILITH selection begins with the complete picture and ends with a clear reason for choosing the individual gemstone. NOBILITH documents lighting conditions, colour-change description, laboratory status and visual evidence so that the gemstone can be understood beyond a single photograph.
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
- 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
- KnowledgeWhat treatment disclosure meansMany 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.Read more
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Updated 2026-09-30