Meetiyagoda — The Sri Lankan Source of Blue-Sheen Moonstone
Meetiyagoda — The Sri Lankan Source of Blue-Sheen Moonstone
The Galle District deposit that has supplied the world's finest moonstone for more than a century
Meetiyagoda is a gem-mining locality in the Galle District of southern Sri Lanka, internationally recognised as the principal source of fine blue-sheen moonstone — orthoclase feldspar exhibiting the floating blue adularescence that defines the variety in its highest expression. The deposit has supplied the international moonstone market for more than a century, with Meetiyagoda material setting the visual benchmark against which moonstone from other localities is measured.
The geology
The Meetiyagoda deposit occurs in deeply weathered pegmatites within the Precambrian metamorphic rocks of southern Sri Lanka. The pegmatites are richly feldspathic, with the orthoclase having undergone the slow subsolvus exsolution that produces the alternating orthoclase-albite lamellae responsible for adularescence. The weathering of the pegmatite host has freed the moonstone crystals from the matrix and concentrated them in the residual soil and clay overburden, which is the principal mining horizon.
Mining at Meetiyagoda is largely artisanal, with shallow shafts and pits worked by hand. Miners follow the moonstone-bearing horizons through the weathered pegmatite, with the recovered material sorted, cleaned, and graded for cabochon cutting. The artisanal character of the production has been a feature of the locality from its earliest commercial development and remains the dominant production model.
The blue sheen and what makes Meetiyagoda material special
Adularescence — the moving, billowy sheen that defines moonstone — arises from light scattering at the boundaries of submicroscopic lamellae of orthoclase and sodium-rich albite within the host feldspar. The colour of the sheen depends on the spacing of the lamellae relative to the wavelengths of visible light: where the spacing is right, shorter wavelengths scatter preferentially, producing the cool blue floating sheen that defines fine blue-sheen moonstone.
Meetiyagoda material is distinguished by the consistency and intensity of its blue adularescence. The lamellar microstructure of the local moonstone is exceptionally well-developed, with the result that the floating blue sheen is more saturated, more visible from a wider range of viewing angles, and less mixed with white or silvery sheen than moonstone from other localities. The body of the stone is typically transparent and colourless, providing a clean ground against which the blue sheen reads at maximum visibility.
The market
Fine blue-sheen Meetiyagoda moonstone commands substantial premiums over the white and silvery moonstone produced from other localities, with sizes above five carats and strong, transparent body becoming markedly rarer. Indian moonstone (from Karur and elsewhere), Madagascan, Tanzanian, and Burmese material together supply the broader moonstone market, but the high-end blue-sheen segment remains dominated by Sri Lankan production.
Origin attribution for moonstone is uncommon on coloured-stone laboratory reports — the species is rarely the subject of formal origin determination — but the trade recognises Meetiyagoda material on visual character and dealer provenance. For high-end purchases, the Sri Lankan attribution typically rests on the dealer's representation and on the established visual signature of the locality's material.
Cutting and care
Cabochon orientation is critical for moonstone: the cutter must align the lamellar planes parallel to the base of the cabochon and orient the dome to maximise the floating sheen as the stone is rotated. A miscut moonstone shows the sheen only in a narrow viewing window, while a properly cut stone shows the sheen across a wide range of angles. The intelligence required for the orientation is one reason the best Sri Lankan production goes to experienced cutters in Sri Lanka, India, and Thailand rather than being exported as rough.
Hardness at 6 to 6.5 on the Mohs scale makes moonstone soft for ring use; pendants, earrings, and protected ring settings (bezel rather than prong) are the preferred mountings. Cleaning is by mild soap and warm water; ultrasonic and steam cleaning are not recommended because of the cleavage characteristic of orthoclase feldspar.