Madagascar sapphirine is the gem variety of the rare magnesium-aluminium silicate species sapphirine, recovered chiefly from granulite-facies metamorphic rocks in the south of Madagascar around Tranomaro, Beraketa, Itrongay and Andrianondambo (a separate locality from the corundum-producing Andranondambo). The name reflects the species' typical sapphire-blue colour and predates its formal characterisation as a distinct mineral.

Material character

The species is a magnesium-aluminium silicate distinct from corundum, despite the colour resemblance. Madagascan stones range from violet-blue and steely blue through teal and green to occasional reddish or purplish examples in pinitic or chromium-rich variants. Pleochroism is moderate; refractive indices fall between roughly 1.70 and 1.73, with biaxial character and a hardness of 7.5. Specific gravity sits near 3.45, useful in separating the species from sapphire and tanzanite at the bench.

Cuttable rough is rare; transparent, clean stones above one carat are notable, and stones above three carats are unusual. Most material is opaque to translucent and finds limited use as cabochon goods. Inclusions and growth features include needles, healed fissures and characteristic granulite-facies mineral inclusions of cordierite, spinel and rutile.

Trade and identification

Sapphirine is unenhanced; no commercial treatment is in regular use. The species is sufficiently rare that supply is dominated by collector channels rather than mainstream jewellery trade. Identification requires laboratory-grade testing because of overlap in body colour with sapphire, kyanite, tanzanite and certain spinel and tourmaline variants; refractive index, biaxial optic figure and Raman spectroscopy resolve the species reliably.

Madagascan sapphirine remains one of the rarest faceted coloured stones available to the collector trade, and the country accounts for the majority of facet-grade material on the market.