The sky of gems
There are some gems that have the extraordinary ability to trap “stars” in their crystal lattice: it is a peculiarity that gives luster and value to all those jewels that mount such stones.
This optical phenomenon is called asterism and is observed mainly in rubies and sapphires, but can sometimes be found in spinels, in some types of garnets and in rose quartz.
Rutile needles oriented according to the crystalline lattice in a Sri Lankan ruby. If the conditions of orientation and interaction with light allow it, you can see by the naked eye that a star will be formed on the surface of the gem.
Photo credits: www.ruby-sapphire.com
The “stars” are visible to our eyes thanks to the presence of a few small rutile needles, a mineral that you can trace in the gem, and that, if oriented appropriately, makes the light go through it and back to our eyes producing this spectacular pattern that recalls the shape of a star, six and – when we are particularly lucky – twelve points.
Only the wisdom of the carver, however, allows the gem to shine all its potential: only the cabochon cuts in fact allow the observation, always for a matter of reflection and interaction of light between rutile and our eye.
It’s not therefore said that to be amazed and open-mouthed it’s necessary to raise your eyes to the sky: sometimes nature is so generous to give us the opportunity to wear a small piece of sky on our neck, wrist or finger.