About Rubies
Ruby is the red gem variety of corundum and, on a per-carat basis, the most valuable coloured gemstone in the world. Where blue sapphire is the gem of kings, ruby is the gem of warriors and lovers — a stone that has been credited across cultures with the power to protect against poison, sharpen the intellect, and inflame the heart. The trace-element responsible for the red colour is chromium, in concentrations of as little as 0.1 to 1.0 per cent by weight; the same chromium that turns corundum red turns beryl green in the case of emerald.
The most coveted ruby colour is described in the trade as “pigeon's blood” — a vivid, slightly purplish red of high saturation with a faint internal fluorescence under daylight that gives the stone an apparent inner glow. This colour is associated above all with the Mogok deposits of Upper Burma (Myanmar), which have produced the finest rubies since at least the fifteenth century. Mogok rubies typically display strong red fluorescence under long-wave UV and an inclusion suite that includes short rutile silk, calcite, and characteristic crystals of pyrrhotite or apatite. The smaller Mong Hsu deposit in northern Shan State, opened in the 1990s, produces a darker, more purplish red that is almost always heat-treated to remove a blue core.
Mozambican ruby, mined commercially at Montepuez since 2009, has now overtaken Burma as the world's leading source by volume. The best Montepuez material rivals fine Burma in colour, and the AGL laboratory in Sri Lanka examines significant quantities of Mozambique rough and polished material every month. Distinguishing Mozambique from Burma is one of the more demanding origin determinations in modern gemology, requiring LIBS trace-element analysis (iron and gallium ratios are particularly diagnostic) combined with careful microscopic examination of the inclusion suite.
Treatment disclosure is critical in ruby certification. The vast majority of commercial rubies have been heat-treated, typically at temperatures between 1,400 and 1,800°C, to improve colour and reduce visible silk. AGL classifies heat-treated rubies as “Indications of heating” on the certificate. A small but commercially important sub-category — rubies that have been fracture-filled with lead glass to fill surface-reaching cracks — receives an entirely separate classification: such stones are described as “Composite ruby” or “Lead-glass-filled ruby,” because the lead glass component is so substantial that the resulting material can no longer be properly described as natural ruby. The Pacific & Indian Ocean trade has seen significant volumes of lead-glass-filled ruby move through retail channels since the early 2000s, and AGL's FTIR protocol detects this treatment immediately.
For collectors of Burmese pigeon-blood ruby, an AGL certificate represents three findings: confirmation of natural ruby (not synthetic, not glass-filled), determination of heat-treatment status (with unheated Mogok material commanding spectacular premiums), and origin determination supported by recorded LIBS and FTIR data. We never issue a Mogok-origin report without analytical confirmation, and we will plainly state “Origin: undetermined” where the evidence does not support a definitive conclusion.
How AGL certifies Rubies
Every rubies submitted to an AGL laboratory is examined by at least two senior gemologists and analysed using our standard instrumental package: refractive-index and specific-gravity measurement, microscopic examination under dark-field and fibre-optic illumination, UV-VIS-NIR absorption spectroscopy, FTIR spectroscopy for treatment detection, and LIBS or ED-XRF for trace-element analysis where origin is in question. Every conclusion on the certificate — species, variety, treatment, origin — is supported by recorded analytical data, and every certificate is recorded in our secure verification database for online authentication at any time.
For full service descriptions and turnaround times, see our Services page, or contact your nearest AGL laboratory for a written quotation.
