Adularescence is the word for the floating, billowing light inside a moonstone. It is the quality that makes the stone worth wearing, and it varies enormously from stone to stone. Some moonstones have a strong, high-sitting blue flash. Others have a diffuse, milky glow that sits deep in the stone. Neither is wrong, but they are different, and knowing what you are looking at helps you choose the right piece.

The optics behind the glow

Moonstone is a feldspar mineral, specifically a variety called orthoclase. It is made up of alternating thin layers of two different feldspar types, albite and orthoclase, which have slightly different refractive indices. When light enters the stone, it scatters between these layers and produces the adularescent glow. The thinner and more regular the layers, the stronger and more blue the adularescence. Thicker, less regular layers produce a more diffuse, white or silver glow.

High versus deep adularescence

A high adularescence sits close to the surface of the stone and moves sharply as you tilt it. A deep adularescence sits further inside and has a softer, more three-dimensional quality. High adularescence is generally considered more valuable in the trade, but deep adularescence can be more interesting to wear because it changes more gradually with movement. The moonstone in our crescent pendant has a strong, high-sitting blue adularescence that is visible in most lighting conditions.

How to judge a moonstone before buying

Hold the stone under a single point light source, ideally a small LED torch or a lamp with a clear bulb. Move the stone slowly from side to side. A good adularescence will roll across the stone in a clean band. If the glow is patchy, or if it only appears in one narrow angle, the layering is uneven. Also look at the stone in diffuse natural light, which will show you the body colour. Moonstone body colour ranges from colourless to grey, peach, and green.

What we look for when sourcing

We source our moonstones from Sri Lankan rough, which is the traditional source for the strongest adularescence. We buy rough or pre-formed cabochons and, where the shape allows, Tiago cuts them in the atelier to optimise the orientation of the layers. The orientation of the cut relative to the layering is what determines whether the adularescence sits high or deep, which is why buying a cut stone from a photograph is always a partial picture.

If you want to see adularescence in person before choosing a piece, a stone sourcing consultation at the atelier is the right step. We keep a selection of loose moonstones in different qualities and can show you the difference side by side.