Moonstone Gemstones

What is a moonstone and what causes its glow?

Moonstone is a feldspar mineral — specifically a variety of orthoclase — whose signature adularescence is caused by the scattering of light between alternating layers of albite and orthoclase within the stone. This optical effect produces a rolling, cloud-like sheen that sits just below the surface rather than reflecting off it. The finest specimens, sourced traditionally from Sri Lanka, display a blue adularescence over a near-colourless body; Indian material tends toward a more orange or rainbow iridescence, while material from Myanmar can show a striking white glow. The intensity of the adularescence depends on the thickness and regularity of those internal layers, which is why no two moonstones read quite the same way under light.

How durable is moonstone for everyday wear?

Moonstone sits at 6 to 6.5 on the Mohs hardness scale, which places it below sapphire, ruby, and most other gemstones commonly set into rings worn daily. It is also vulnerable to cleavage — meaning a sharp blow at the right angle can cause it to split along its internal planes. For this reason, moonstone is best suited to occasional-wear pieces: pendants, earrings, dress rings worn for events, or cocktail rings that are removed during manual tasks. When moonstone is set into a ring at our Hatton Garden workshop, a bezel or half-bezel setting is often recommended, as it wraps the girdle and reduces the risk of chipping at the edges. A protective setting does not eliminate wear risk entirely, but it meaningfully extends the stone's lifespan in a mounted context.

What does a moonstone gemstone cost in the UK?

Moonstone is generally among the more accessible gemstones by price per carat, though high-quality blue adularescent Sri Lankan material commands a significant premium over lower-grade Indian or Brazilian stones. The key value drivers are the intensity and colour of the adularescence (blue over colourless being the most valued), the clarity of the body, the quality of the cut — a well-placed cabochon dome positions the adularescence centrally — and the overall size. A well-cut moonstone of 1.0ct to 2.0ct with strong blue adularescence will cost considerably more than a similarly sized stone with weak or uncentred optical effect. Setting costs are additional; when a loose moonstone is set into one of our rings, the 7–14 working day lead time for the ring applies from order confirmation.

How is moonstone cut and what shapes are available?

The vast majority of moonstones are cut as cabochons — smooth, domed ovals or rounds — because the cabochon form is what centres and displays the adularescence most effectively. Faceting a moonstone tends to fragment the optical effect, breaking the billowing sheen into competing reflections. The dome height is critical: too flat and the adularescence sits near the girdle rather than at the apex; too high and the stone becomes prone to damage and sits proud in any setting. Oval cabochons in proportions of roughly 2:1 length to width are the most commonly available moonstone form, though round, pear, and freeform shapes exist, particularly in higher-carat material. Each moonstone we supply carries a certificate of authenticity confirming its identity and, where applicable, its origin.

How to care for and store moonstone

Moonstone should be stored separately from harder stones — a fabric-lined pouch or individual compartment prevents contact with diamonds, sapphires, or other materials that can scratch it. Cleaning is best done with warm water, a mild soap, and a soft cloth; ultrasonic and steam cleaners should be avoided entirely, as vibration can propagate along moonstone's cleavage planes and cause internal fracturing that is not immediately visible. Prolonged exposure to harsh chemicals — cleaning products, chlorine, acids — should also be avoided. When moonstone is set into a ring, the London Assay Office hallmark applied to the metal at completion provides a formal record of the setting's metal standard, though the stone itself carries its own certificate of authenticity as a separate document.