Grey Moonstone

Moonstone is a variety of feldspar, the most common group of minerals in the Earth's crust. According to GIA, feldspars make up more than half of the crust's rock. So what is special about this stone? The light.

As the stone forms, two minerals, orthoclase and albite, separate into thin layers stacked on top of each other. These layers are about as thin as a wavelength of light, so they scatter it. The result is a soft glow that seems to float just under the surface and moves as you turn the stone. This effect is called adularescence. To see it you need good light and a little patience: turn the stone slowly.

Moonstones come in many colors: colorless, white, grey, green, peach and brown. In a grey stone the glow is less striking than in a clear one, but it has something understated and smoky about it, like the moon behind a cloud.

The Romans believed moonstone was made of solidified moonbeams, and both the Greeks and the Romans linked it to their moon goddesses. In the Art Nouveau period it came back into fashion thanks to designers such as René Lalique.

One more fun fact: in 1970 Florida chose moonstone as its official state gem, to commemorate the Moon landings launched from Kennedy Space Center. Moonstone does not occur naturally in Florida. Then again, neither does the Moon.