The Black Prince’s Ruby in the British Crown Jewels is a spinel. So is the Timur Ruby in the collection of Queen Elizabeth II. Both were assumed to be rubies for centuries, a confusion that was not accidental. Spinel and corundum share similar colours, similar geological environments and often the same mine. The difference lies in chemistry: spinel is magnesium aluminium oxide, while corundum is aluminium oxide. That distinction mattered little to merchants selling red stones in medieval Persia.
Why spinel was undervalued for so long
The 1962 revision to the Gemological Institute of America’s classification system formally separated spinel from ruby and sapphire for grading purposes, but market perception lagged. Spinel was sold as a second-tier stone, not as interesting as sapphire, not as valuable as ruby, despite having physical properties that rival both. Hardness of 8 on the Mohs scale. Singly refractive, which means no doubling of inclusions and exceptionally clean optics. And a colour range that spans vivid red, intense pink, brilliant cobalt blue, violet, orange and grey-black.
Burmese spinel and the Mogok benchmark
The finest spinels come from the same valley as Burma’s finest rubies: Mogok, in northern Myanmar. Mogok spinel, particularly in vivid red and hot pink, has established itself as the benchmark against which other origins are measured. Vietnamese spinel from Luc Yen produces comparable material and is increasingly sought. Sri Lankan spinel covers a wider colour range including some of the finest cobalt blues. Tajikistan’s Kuh-i-Lal deposit has supplied red spinel since antiquity and continues to yield stones of historical significance.
Spinel vs sapphire: the collector’s argument
Collectors with gemmological knowledge have been buying fine spinel over commercial sapphire for two decades, primarily because superior material is available at lower prices, and because treatment rates are dramatically lower. The vast majority of spinel on the market is unheated and untreated. There is no equivalent of the beryllium diffusion or fracture filling that affects so much commercial corundum. This means that a documented natural unheated spinel is exactly what it appears to be, without the treatment screening complexity that fine ruby and sapphire require. For serious collectors, that simplicity has significant value.
Identification markers
Spinel’s single refraction is one of its most useful identification tools. Under the polariscope, it shows an anomalous extinction pattern, but unlike doubly refractive stones, it does not show true birefringence. Refractive index sits around 1.712–1.762 depending on composition. The spectrum under a hand spectroscope shows a distinctive chromium absorption in red and pink stones. Inclusions in Burmese spinel often include octahedral negative crystals and fine silk, useful for confirming origin when supported by laboratory analysis. No reliable field test separates Burmese from Vietnamese origin definitively; that requires laboratory instrumentation.
The market trajectory
Fine spinel prices have risen significantly since 2015. A top Burmese red spinel of two carats with laboratory certification now trades at $3,000–8,000 per carat at wholesale, with exceptional material exceeding this range. Blue cobalt spinel, particularly from Sri Lanka, commands premiums reflecting its rarity within an already rare species. The caveat is liquidity: spinel remains a specialist market. A dealer who actively trades fine ruby and sapphire is the right counterparty; a general jewellery buyer is not. As the stone builds a track record among collectors, this is likely to change, but it has not fully changed yet.