Reading a GRS Report: Pigeon's Blood, Royal Blue, Vivid and the Comments Line
By the Byrex Gems team, Toronto · Published 21 October 2026
A GRS report states identification, weight, colour, a comments line on treatment and an origin opinion, and applies its trademarked GRS-type pigeon's blood and royal blue terms by criteria that differ from those of Gübelin and SSEF. Here is how to read each line before buying on it.
A GRS report is a gemstone identification report from GRS GemResearch Swisslab, the Swiss laboratory founded in 1996 by Dr Adolf Peretti. It states what the stone is, its weight and measurements, a colour graded against master stones, a comments line on treatment such as "No indication of thermal treatment" or an H code for a heated stone, and an opinion on geographic origin. Its best-known lines are the colour terms GRS has trademarked, GRS-type "pigeon's blood" for rubies and GRS-type "royal blue" for sapphires, each defined by GRS's own criteria and subdivided since late 2017 by the word vivid. Those criteria differ from the ones Gübelin Gem Lab and SSEF apply to the same words.
This guide reads the report line by line and ends with a checklist for jewellers who buy rubies and blue sapphires on GRS paper.
Who GRS is and what its report states
GRS describes itself as an independent research laboratory specialising in the origin of rubies, sapphires and emeralds, with offices in Switzerland, France, Hong Kong, Thailand and the United States. Its reports are common in the ruby and sapphire trade and at auction. A Sotheby's Hong Kong catalogue note from 2016 cites a GRS report stating that a set of sapphires are natural, of Burmese (Myanmar) origin, of vivid blue colour, GRS-type royal blue, with no indication of thermal treatment (Sotheby's, lot 1690).
The main page gives the identification (natural ruby, natural sapphire), weight, dimensions, shape and cut, colour, a comments line and the origin opinion. GRS calls the document a professional opinion based on the data collected on the day of examination, with colour graded against master sets, treatment tested instrumentally and origin given as a "place of origin opinion". Read three lines first: colour, comments (the treatment statement) and origin (an opinion, not a certificate of provenance).
Pigeon's blood, royal blue and vivid, as GRS defines them
GRS grades ruby colour in daylight against master sets on a five-step scale: pinkish red, red, intense red, vivid red and deep red. GRS-type "pigeon's blood" is reserved for rubies in the vivid red range with high intensity and low tone, no brown or orange overtone, and medium to strong fluorescence under long-wave ultraviolet light, which GRS links to high chromium and little iron (GRS on pigeon's blood). The grade is independent of origin, so Mozambique and Madagascar rubies can qualify alongside Burmese stones. Heated rubies without residues can qualify; GRS withholds the term from rubies with more than minor heating residues, from beryllium-treated and lead-glass-filled stones, and from synthetics.
Since late 2017 GRS has subdivided the field into three descriptors, "intense to vivid red", "vivid red" and "vivid to deep red", each of which can carry the GRS-type term. A stone can be graded in that range without the term because of colour zoning, a window, or beryllium or diffusion treatment. A ruby of the right colour but weaker fluorescence receives an appendix calling it reminiscent in colour saturation of a GRS-type pigeon's blood ruby, without strong fluorescence; the appendix is not the grade. Royal blue follows the same structure for sapphires, with the GRS-type "royal blue" term for stones within GRS's master-stone range (GRS colour terms).
How Gübelin and SSEF use the same words
The other two Swiss laboratories use "pigeon blood red" and "royal blue" with stricter conditions. In 2015 Gübelin Gem Lab and SSEF harmonised their criteria: an intense, saturated and homogeneous red or blue within ranges set by master stones; for pigeon blood red, strong fluorescence under ultraviolet light and no blue or brown modifier, with a minute purplish tint allowed; and, for both terms, no treatment of any kind, so heating or fissure filling disqualifies a stone (Gübelin Gem Lab colour terms). Stones must also be relatively clean, with even colour; size is not a criterion.
The practical differences are two. A heated ruby can be GRS-type pigeon's blood but never pigeon blood red at Gübelin or SSEF. And a ruby of the right colour without strong fluorescence gets a "reminiscent of" appendix at GRS, while Gübelin uses its own term, crimson red. The words look alike; the stones need not be, which is why the issuing laboratory is named on every Byrex stone page.
The comments line: heated, residues and the H codes
"No indication of thermal treatment" means GRS found no evidence, such as altered inclusions, that heat was applied. "H" means enhanced by heat with no residues. H(a) means insignificant residues within fissures; H(b), minor residues within fissures only; H(c), a transitional grade; H(d), significant and deep-reaching residues in fissures and cavities. H(Be) means heat with light elements such as beryllium, and PHT means pressure and high temperature (GRS enhancement disclosure). Other phrases are descriptive: "Non-enhanced clarity features present" records empty or dried-out fissures; "Color grading not applied" means those features were graded prominent, so no GRS-type colour applies; CST 1 to CST 4 records a colour stability test on padparadscha, yellow and orange sapphires.
The LMHC laboratories, which include GIA, Gübelin Gem Lab and SSEF but not GRS, use different harmonised wording: "No indications of heating", "Indications of heating (no residue)", and minor, moderate or significant residue in healed fissures (LMHC Information Sheet 1). Our article on heated versus unheated sapphire covers what the difference is worth.
Origin, appendices and the Platinum award
The origin line is an opinion that names a country or traditional trade region, not a mine. Burma (Myanmar) covers the Mogok and Mong Hsu deposits, the classic source of Burma rubies. Mozambique means, in practice, Montepuez, found in 2009 and described by GIA as the world's most productive source of gem-quality ruby. Ceylon (Sri Lanka) is the classic metamorphic sapphire source. Kashmir names the Himalayan mines worked mainly in the 1880s; a Kashmir sapphire on a single report deserves a second opinion.
Appendix pages add information that is not a grade: the colour stability types, the "Vibrant" brilliancy type for stones cut to ideal proportions, the Old Mine / Muzo and "Mariposa" appendices for emerald, and the "reminiscent of pigeon's blood" appendix above. The GRS Platinum Rarity Gemstone Award is a premium report, classified Important or Magnificent, offered at GRS's discretion to stones it judges exceptionally rare against its database and auction records. It signals rarity in GRS's judgement; it changes neither the colour grade nor the treatment line.
Verifying the report, and a checklist before buying
GRS offers free online verification: scan the QR code on the report, or enter the report details exactly as printed into the form on the GRS website. The system covers reports from 2000 onwards; earlier reports must be sent to GRS. Verification confirms the report exists; it does not re-examine the stone.
- Read the colour line in full, noting any GRS-type term and its vivid descriptor.
- Translate the H code in the comments line: heated with no residues is not the same as minor or significant residues.
- Treat the origin line as an opinion; ask for a second laboratory where origin drives the price.
- Check for an appendix; "reminiscent of", colour stability and Platinum mean different things.
- Verify the report online and match weight and dimensions to the stone; a report issued before late 2017 predates the vivid descriptors.
- See the stone, or its video, before comparing on wording.
Rubies and sapphires from Byrex Gems
Byrex Gems has served the jewellery trade from Toronto since 1988, and more than seven thousand jewellers, designers and dealers have bought from us. Many of our rubies and sapphires carry GRS, SSEF, Gübelin or Lotus reports; each stone page quotes the report wording as issued, and GRS-certified stones show an image of the GRS report itself. Every stone is filmed in our office, unedited, so what you see is what arrives. Approved trade buyers see prices online. A message on WhatsApp at +1 (437) 450-3786 is answered within hours, and an email to info@byrex.com the same day, seven days a week.
What is listed is a part of what we hold; more is kept in the vault, and what we do not hold we can source through our offices worldwide. See our pigeon's blood rubies and royal blue sapphires, or use Stone Search to filter by colour and treatment. Private viewings are by appointment in Toronto, Hong Kong, Bangkok and Dubai.