Beautifully set into Sterling Silver, Amethyst measurement is approx.  1 inch.  Chain included.
 

7th chakra (crown) Opens spiritual awareness and awakening. Increases self-worth and spiritual peace. Aids in meditation, eases stress, helps insomnia. Use on the crown chakra to facilitate visualization and past life recall. Amethyst points have been used in native american spiritual ceremonies to consecrate the circle and to provide power to the tribe. 
This is a great crystal to help those begin their meditation classes, I find the clear purple ray to boost the opening of the third eye.  This will allow you to understand the spiritual plane of existence. These crystals are very powerful with excellent color.