Moonstone

Beneath the surface of this feldspar, a haunting sheen moves like moonlight shining in water.

FACTS

Feldspar is prized for its wavy blue adularescence caused by light scattering by the growth of microscopic, alternating layers. A favorite gem of many Art Nouveau jewelry designers.

Moonstone is a variety of orthoclase from a group of feldspars. During molding, orthoclase and albite separate into alternating layers. When light falls between these thin layers, they scatter and create a phenomenon called adularescence. Adularescence is light that appears to be rippling through a gemstone. Other feldspar minerals may also exhibit adularescence, including labradorite and sanidine.

The subtle beauty of Moonstone and its long-standing heritage make it probably the most famous member of a group of feldspar-quality feldspars.

Feldspars are the most abundant minerals in the earth’s crust, as well as some of the most diverse. You can take the stone anywhere in the world and you will probably find that it contains a mineral or two from a group of feldspars.

Moonstone is a variety of orthoclase from a group of feldspars. It consists of two feldspar minerals, orthoclase and albite. First, the two minerals are mixed. After the newly formed mineral cools, the overgrown orthoclase and albite separate into stacked, alternating layers.

When light falls between these thin flat layers, it scatters in many directions and creates a phenomenon called adularescence. Adularescence is light that appears to propagate through a gemstone and gives its surface a radiant appearance.

Perhaps the most compelling aspect of adularescence is the appearance of movement. The hazy light seems to roll on the surface of the gemstone as you change your perspective.

Other feldspar minerals may also exhibit adularescence. One of them is labradorite feldspar, which is found mainly in Labrador, Canada. Another labradorite – found in Madagascar – has a multicolored adularescence on the light body color. It is known in the trade as the rainbow moonstone, although it is actually a variety of Labradorite rather than orthoclase.

Sanidine is another feldspar mineral that can include adularescent gems called moonstones. To call a moonstone, the true identity of a mineral is not as important as the beauty of its adularescence.