The CIBJO Coloured Stone Book is the volume within the CIBJO Blue Book series that establishes internationally recognised standards for the nomenclature, classification, grading, and treatment disclosure of coloured gemstones. Published and periodically revised by CIBJO — the World Jewellery Confederation (Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie des Diamants, Perles et Pierres) — it serves as the authoritative reference against which national trade associations, gemological laboratories, and jewellery businesses worldwide align their terminology and disclosure practices. Alongside the Diamond Book and the Pearl Book, the Coloured Stone Book forms the core of the Blue Book framework, which collectively constitutes the most widely adopted international standard for the jewellery trade.

Background and Purpose

CIBJO was founded in 1926 and has long pursued the harmonisation of trade practices across its member nations. The need for a unified coloured-stone standard became acute as global commerce in rubies, sapphires, emeralds, and a widening array of other species expanded through the latter half of the twentieth century. Without common definitions, the same material could be described differently by sellers in Bangkok, dealers in Antwerp, and retailers in New York — creating confusion for consumers and legal uncertainty for the trade. The Coloured Stone Book addresses this by codifying the language of the gem trade: which names are permissible, how treatments must be disclosed, and how synthetic and imitation materials must be distinguished from their natural counterparts.

The document is not a grading system in the narrow sense of assigning letter grades or numerical scores to individual stones. Rather, it establishes the vocabulary and disclosure framework within which any grading or description must operate. It is, in effect, a constitutional document for coloured-stone commerce.

Nomenclature and Classification

A central function of the Coloured Stone Book is the regulation of gemstone names. The standard distinguishes between:

• Species — mineralogically defined groups, such as corundum, beryl, or tourmaline.
• Varieties — named subdivisions of a species, typically defined by colour or optical phenomenon, such as ruby and sapphire within corundum, or emerald and aquamarine within beryl.
• Trade names — commercial designations that may be used only when their relationship to the correct mineralogical name is clearly stated, preventing misleading usage such as calling green glass "emerald" or green tourmaline "Brazilian emerald" without qualification.

The Coloured Stone Book explicitly prohibits the use of variety names from one species as unqualified descriptors for another. A blue topaz may not be sold simply as "aquamarine," and a synthetic ruby must be identified as synthetic. This nomenclature discipline protects consumers and maintains the integrity of the market for natural, untreated, or minimally treated stones.

The standard also addresses phenomenal stones — those exhibiting asterism, chatoyancy, colour change, or adularescence — requiring that the phenomenon be accurately described and that any trade name applied be consistent with the stone's actual mineralogical identity.

Treatment Disclosure

Treatment disclosure is arguably the most commercially consequential section of the Coloured Stone Book. The standard operates on a tiered disclosure model that reflects both the prevalence and the permanence of various treatments:

• Heat treatment — the most widespread enhancement in the coloured-stone trade, applied routinely to corundum, tanzanite, aquamarine, and many other species. The Coloured Stone Book requires disclosure when heat treatment is detectable, while acknowledging that in certain species — most notably sapphire and ruby — heating is so universal that its presence is assumed unless a laboratory report explicitly confirms the stone to be unheated.
• Fracture filling and clarity enhancement — the introduction of glass, resin, or oil into surface-reaching fractures, as practised with emeralds (cedar oil or synthetic resins) and, more controversially, with lead-glass-filled rubies. The standard requires clear disclosure of all such treatments, with distinction made between traditional and minor oiling (considered acceptable with disclosure) and more significant filling with non-traditional substances (requiring explicit statement).
• Irradiation — used to alter colour in blue topaz, certain tourmalines, and other species. The Coloured Stone Book requires disclosure, and the standard notes that some irradiated colours are stable while others may fade.
• Coating and surface treatments — thin films or surface applications that alter apparent colour or lustre. These require disclosure as they are generally considered non-permanent and may affect value assessment.
• Dyeing — the introduction of colourants into porous or fractured material, common in jade, chalcedony, and some lower-grade corundum. Full disclosure is mandatory.
• Beryllium diffusion — lattice diffusion of beryllium into corundum to produce padparadscha-like or vivid orange-yellow colours, a treatment that became commercially significant in the early 2000s. The Coloured Stone Book addresses diffusion treatments as a category requiring explicit disclosure, given that the colour modification penetrates the stone at a lattice level and is not detectable by standard visual inspection.

The standard employs a graduated language of disclosure, distinguishing between treatments that are considered minor and stable (and therefore require only routine notation) and those that are significant, unstable, or value-altering (and therefore require prominent, specific disclosure). This hierarchy reflects the practical reality of the trade while maintaining consumer protection as the overriding principle.

Synthetic and Imitation Materials

The Coloured Stone Book draws a clear and legally significant distinction between three categories of material:

• Natural gemstones — formed by geological processes without human intervention, though they may have been treated after recovery.
• Synthetic gemstones — materials that share the chemical composition, crystal structure, and optical properties of a natural counterpart but are produced in a laboratory or industrial setting. Examples include synthetic ruby (Verneuil, Czochralski, or flux-grown), synthetic emerald (flux or hydrothermal), and synthetic alexandrite. The standard requires that the word "synthetic" precede the gemstone name in all trade and consumer communications.
• Imitation or simulant materials — substances that resemble a natural gemstone in appearance but differ in chemical composition and structure. Glass, cubic zirconia used to simulate diamond or coloured stones, and synthetic spinel used to simulate aquamarine all fall into this category. The standard prohibits the use of the natural stone's name, qualified or otherwise, for an imitation.

This tripartite framework is foundational to consumer protection law in many jurisdictions and is directly referenced in trade regulations across the European Union, the United States, and numerous Asian markets.

Origin Determination

Geographic origin — whether a ruby is from Mogok, Mozambique, or Mong Hsu; whether a sapphire is from Kashmir, Ceylon, or Madagascar — carries significant market implications and can affect value by multiples. The Coloured Stone Book acknowledges the commercial importance of origin determination while maintaining that origin is a separate matter from species identification and treatment disclosure. The standard does not itself define origin-determination methodology, which falls within the remit of individual gemological laboratories, but it establishes that any origin statement must be clearly identified as such and must be based on scientific examination rather than commercial assumption.

Relationship to Gemological Laboratories and Trade Bodies

The Coloured Stone Book is not a legally binding instrument in most jurisdictions, but its influence is pervasive. Major gemological laboratories — including the Gemological Institute of America (GIA), the Swiss Gemmological Institute (SSEF), Gübelin Gem Lab, and the Gemmological Association of All Japan (GAAJ) — align their reporting terminology and disclosure language with CIBJO standards, ensuring that a laboratory report issued in Lucerne is intelligible to a buyer in Singapore or a court in London. National trade associations in CIBJO's member countries frequently incorporate the Blue Book standards into their codes of conduct, making compliance a condition of membership.

The American Gem Trade Association (AGTA) maintains its own Source Code for treatment disclosure, and the GIA publishes its own grading standards; both are broadly consistent with the CIBJO framework, reflecting the degree to which the Coloured Stone Book has shaped global industry norms even where it is not formally adopted by name.

Revisions and Updates

The Coloured Stone Book is a living document. CIBJO's Coloured Stone Commission reviews and revises the standard periodically to address new treatments, newly commercialised gem materials, and evolving market practices. The emergence of beryllium-diffused corundum in the early 2000s, the proliferation of lead-glass-filled rubies from approximately 2004 onwards, and the growing trade in synthetic coloured stones produced by improved hydrothermal and flux methods have each prompted revisions or clarifying addenda. The most recent publicly available versions of the Blue Book documents are maintained on the CIBJO website and are available for download by trade members and the public alike.

Significance for the Trade and Consumer

For the professional trade, the Coloured Stone Book provides a common language that reduces dispute and facilitates cross-border commerce. For the consumer, it underpins the disclosure obligations that make informed purchase decisions possible. A stone described on a laboratory report or invoice in terms consistent with the Coloured Stone Book carries a defined meaning: the treatment disclosures are standardised, the nomenclature is controlled, and the distinction between natural, synthetic, and imitation is unambiguous. In a market where a single untreated Burmese ruby of fine colour can command a price per carat exceeding that of a fine diamond, the precision of that language is not merely academic — it is the foundation of value itself.

Further Reading

• CIBJO Blue Book documents (official CIBJO website)
• Gems & Gemology, GIA — treatment and nomenclature research
• AGTA Source Code for treatment disclosure