A ghostly sheen moves under the surface of this feldspar, like moonlight glowing in water.

Moonstone, renowned for its delicate beauty and rich heritage, is arguably the most recognizable gem-quality member of the feldspar group.

Feldspars are the most prevalent minerals in the Earth's crust and are remarkably diverse. Most rocks around the world contain feldspar minerals.

Moonstone is a variety of the feldspar mineral orthoclase and is composed of orthoclase and albite. Initially, these two minerals are intermingled, but as the mineral cools, they separate into alternating layers of orthoclase and albite.

When light interacts with these thin, stacked layers, it scatters in various directions, creating the phenomenon known as adularescence. This effect causes a glowing, billowing light to move across the surface of the gemstone.

One of the most enchanting features of adularescence is its dynamic appearance. The misty light seems to glide across the gem's surface as you change your viewing angle.

Other feldspar minerals can also exhibit adularescence. For instance, labradorite, found primarily in Labrador, Canada, can display this effect. A variant of labradorite from Madagascar, known as rainbow moonstone, features multi-coloured adularescence over a lighter body colour, though it is technically not orthoclase moonstone.

Sanidine, another feldspar mineral, can also produce adularescent gems that are referred to as moonstones. Ultimately, whether a mineral is classified as moonstone depends more on the beauty of its adularescence than on its specific mineral identity.