Coloured Stone Identification Report

The laboratory document that establishes what a gemstone is, where it may have formed, and what has been done to it

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A coloured stone identification report is a formal laboratory document that confirms the species, variety, and treatment status of a gemstone. Unlike diamond grading reports — which assess cut, colour, clarity, and carat weight on standardised scales — a coloured stone identification report makes no quality judgements. Its purpose is strictly one of material identity and disclosure: is this stone natural or synthetic? Is it the species it purports to be? Has it been subjected to heat, fracture filling, diffusion, irradiation, or any other detectable enhancement? These questions underpin every serious trade transaction involving rubies, sapphires, emeralds, alexandrites, and the full range of coloured gem species, and the identification report is the instrument through which they are answered.

What the Report Covers

A standard coloured stone identification report addresses four core questions:

Species and variety. The report confirms the mineral species (e.g., corundum, beryl, chrysoberyl) and, where applicable, the variety (ruby, blue sapphire, emerald, alexandrite). This determination rests on a convergence of physical and optical constants measured in the laboratory.
Natural versus synthetic origin. The report distinguishes stones formed by geological processes from those produced by laboratory methods such as the Verneuil flame-fusion process, the Czochralski pulling method, hydrothermal synthesis, or flux growth. Inclusions, growth structures, and spectroscopic signatures are the primary discriminators.
Treatment status. The report discloses any enhancements detected, or confirms their absence. This is frequently the most commercially significant section of the document.
Geographic origin (where offered). Many leading laboratories now include a geographic origin opinion on the same document or as a supplementary service. Origin is not always part of a basic identification report, but it has become increasingly integrated because provenance can substantially affect value — particularly for Burmese rubies, Kashmir sapphires, and Colombian emeralds.

Standard Analytical Methods

The conclusions on an identification report are reached through a battery of tests, the exact combination varying by laboratory and by the complexity of the stone under examination.

Refractive index (RI). Measured with a refractometer, RI is a fundamental optical constant that narrows identification to a small group of candidate species. Corundum, for example, shows a characteristic doubly refractive reading in the range of approximately 1.762–1.770.
Specific gravity (SG). Hydrostatic weighing or heavy-liquid comparison provides the density of the stone, further constraining species identification. Corundum's SG of approximately 4.00 distinguishes it from many simulants.
Spectroscopy. Ultraviolet-visible (UV-Vis) spectroscopy, infrared (IR) spectroscopy, and Raman spectroscopy are now standard tools. UV-Vis reveals the chromophores responsible for colour and can expose certain treatments; IR identifies polymer or glass fillings in fractures; Raman spectroscopy provides a molecular fingerprint that can confirm species and detect foreign materials within inclusions. Advanced laboratories also employ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to measure trace-element chemistry, which is particularly valuable for origin determination and for identifying certain diffusion treatments.
Inclusion examination. Microscopic study of internal features — growth zoning, mineral inclusions, fluid inclusions, fractures, and their relationship to any filling materials — remains indispensable. Synthetic stones grown by different methods leave characteristic growth structures (curved striae in Verneuil material, chevron zoning in flux-grown stones, nail-head spicules in hydrothermal synthetics) that trained gemmologists can identify under magnification.
Fluorescence examination. Long-wave and short-wave ultraviolet fluorescence responses, while not diagnostic in isolation, contribute to the overall picture and can flag anomalies warranting further investigation.

Treatment Disclosure

Treatment disclosure is the section of a coloured stone identification report with the greatest commercial consequence. The major treatments encountered across the coloured stone trade include:

Heat treatment. Applied to corundum, tanzanite, aquamarine, and many other species to improve colour and clarity. Heat treatment of ruby and sapphire is so prevalent that laboratories distinguish between stones with no indications of heating, stones with indications of heating, and — in some reporting systems — stones with evidence of heating with residues (such as flux healing of fractures), which represents a more significant enhancement.
Fracture filling. Glass, resin, or oil filling of surface-reaching fractures is routinely detected via IR spectroscopy and microscopy. Emerald oiling and resin impregnation are industry-standard practices, but the degree of filling is commercially relevant; laboratories such as GIA and the American Gemological Laboratories (AGL) use descriptive scales ranging from "insignificant" to "significant" or "prominent."
Beryllium diffusion. Lattice diffusion of beryllium into corundum, a treatment that emerged in the early 2000s, can dramatically alter colour and is undetectable without LA-ICP-MS analysis. Its discovery prompted laboratories to expand their analytical protocols significantly.
Irradiation. Applied to certain yellow and orange sapphires, topaz, and other species. Stability of the induced colour is a concern and is noted on reports where relevant.
Coating and surface treatments. Thin surface films applied to improve colour or lustre are typically detected by microscopy and may be noted on the report.

The language used to describe treatment status has been the subject of ongoing standardisation efforts within the industry. The Laboratory Manual Harmonisation Committee (LMHC), whose members include GIA, Gübelin Gem Lab, SSEF Swiss Gemmological Institute, Gemmological Institute of Thailand (GIT), and others, has worked to align terminology so that a buyer comparing reports from different laboratories encounters consistent disclosure language.

Issuing Laboratories

Several laboratories have established international reputations for coloured stone identification work:

GIA (Gemological Institute of America) issues its Colored Stone Identification Report (sometimes abbreviated CIR in trade shorthand), which covers species, variety, natural or synthetic origin, and treatment status. Geographic origin is available as an additional service on a separate report.
Gübelin Gem Lab (Lucerne) is widely regarded as one of the most rigorous authorities on origin determination and has been issuing coloured stone reports since 1923. Its reports are particularly respected in the high-value ruby and sapphire market.
SSEF Swiss Gemmological Institute (Basel) is another Swiss authority whose reports carry significant weight in the trade, especially for Kashmir sapphires and Burmese rubies.
American Gemological Laboratories (AGL) is the leading United States laboratory for coloured stones and is known for its detailed treatment grading scales and comprehensive origin opinions.
Lotus Gemology (Bangkok) has rapidly built a strong reputation, particularly for corundum from Southeast Asian and East African sources, and publishes extensively on gemmological methodology.

The choice of laboratory matters in the market. For a Burmese ruby of significant size, a report from Gübelin or SSEF — or ideally both — is frequently required by major auction houses and private collectors. GIA reports are broadly accepted across the trade. For stones destined for the Thai or Southeast Asian wholesale market, GIT reports are common.

What the Report Does Not Cover

It is important to understand the scope limitations of a coloured stone identification report. The document does not assign a quality grade, assess cut proportions, evaluate clarity on a standardised scale, or provide a monetary valuation. Colour descriptions, where included, are observational rather than graded — a report may note "blue" or "violetish blue" as a descriptive term, but this is not a colour grade in the sense that GIA's diamond colour scale is a grade. For quality opinions and value assessments, separate services — such as AGL's "Prestige Gemstone Report" or Gübelin's premium reports — are available, but these go beyond the scope of a basic identification document.

Role in the Trade

In the contemporary coloured stone market, a laboratory identification report has become a near-prerequisite for significant transactions. Major auction houses — Christie's, Sotheby's, Bonhams, and Phillips among them — require laboratory reports for coloured stones above certain value thresholds, and the presence or absence of a report, as well as which laboratory issued it, directly affects bidder confidence and realised prices. In the wholesale trade, dealers routinely request reports before purchasing stones above a few thousand dollars in value, and the cost of obtaining a report is factored into pricing at the outset.

The report also serves a legal and ethical function. In many jurisdictions, failure to disclose known treatments constitutes misrepresentation. A laboratory report creates a documented record of treatment status at the time of examination, providing both buyer and seller with a degree of protection. Trade organisations including the International Colored Gemstone Association (ICA) and the American Gem Trade Association (AGTA) maintain codes of ethics requiring treatment disclosure, and laboratory reports are the primary mechanism through which that disclosure is substantiated.