Moonstone with that appropriately ethereal quality.
It looks like soft, flowing fabric, even silk, yet is as hard as rock.
How does nature do it?
Well, moonstone is a feldspar, like fluorite, and its name derives from the light diffraction that made the Romans believe it was born from solidified rays of the moon.
It has been used in jewellery for millennia, and became particularly popular during the Art Nouveau period. Today, it is the state gem for Florida to commemorate the moon landings, which took off from there.