I had this piece custom made, since I had a tattoo of the same design on my right under arm area. It's the symbol of the Philosopher's Stone or also unofficially known as the Mental Alchemy symbol. 

It's hand made with copper wire with a small deep blue chrysoprase stone in the middle. 

The other necklace I love is this handmade, gold wire wrapped tiger's eye crystal stone. I love how the stone just shines under the light. Since I'm a Capricorn sun and moon, it's a stone associated with this astrological sign.

What's your favorite crystal or stone?