Madagascar ruby is corundum coloured red by chromium, recovered from a series of geologically distinct deposits across the country. Madagascar emerged in the early 21st century as one of the most significant new ruby sources in the world, with finds at Vatomandry (2000), Andilamena (2005), Didy (2012) and the long-running deposits in the Ambatondrazaka and Moramanga area producing both fine quality and large quantity.

Material character

The character of Madagascan ruby varies markedly by deposit. Andilamena material is generally a brownish to purplish red with strong silk and is the bulk of the commercial supply; much of it is heat-treated, often with flux assistance, to clear the silk and improve colour. Didy ruby, in contrast, has been compared in trade circles with classic Mozambique and even Mogok material, with cleaner, more saturated colour and a higher proportion of fine stones, although production has been intermittent and small in scale. Vatomandry produced limited but high-quality stones in the early 2000s.

Refractive index, specific gravity and absorption spectra fall within the standard ruby range. Trace-element fingerprints (iron, titanium, chromium, gallium and vanadium) allow major laboratories to separate Madagascan ruby from Mozambican, Burmese and Thai material with reasonable confidence, although overlap with East African material can complicate origin calls on heated goods.

Treatment and trade

Heat treatment, including flux-assisted heating that fills surface-reaching fissures with residue, is widespread in commercial Madagascan ruby. Disclosure of treatment is required under all major laboratory and trade-association guidelines. Beryllium diffusion has historically been documented in some lots, although the practice has declined in well-regulated channels. Untreated Didy stones with fine colour have brought significant premiums at auction.