Moonstone
Moonstone
Moonstone is a feldspar, most often orthoclase (or a mixture of similar feldspars), prized for its milky luster and shimmering reflection known as adularescence. This optical effect is not simply a "color": it arises from the diffraction and scattering of light within very thin internal layers, formed by alternating layers of slightly different composition. When the stone is well cut, this shimmer glides across the surface like a glow, giving the impression of a lunar halo. Moonstones are found in several regions of the world, notably Sri Lanka and India, as well as in other deposits where feldspars crystallize slowly.
With a hardness of approximately 6 to 6.5 on the Mohs scale, it is less hard than quartz and can be scratched if worn carelessly. It also exhibits pronounced cleavage (typical of feldspars), meaning that an impact can sometimes cause a crack along natural planes. Variations in transparency and color—pearly white, cream, bluish-gray, sometimes peach—depend on the internal structure and the size of the lamellae responsible for adularescence. Lapidaries often favor a cabochon cut, as it highlights the play of light and its "movement." Some stones even display a slight "cat's eye" effect when the internal structures are oriented in a particular way.
For care, gentle cleaning with warm soapy water and a cloth is best, avoiding ultrasound, steam, and impacts. What makes moonstone so fascinating is the direct link between its microstructure and its beauty: a play of light created by the crystal's intricate organization. Each reflection tells a story of slow cooling, layer alignment, and optical physics—a small scientific phenomenon to wear every day.