We shouldn't have favourites I know,  but none the less Amethyst is still my favourite 'go to crystal' & one of the main healers.
This amazing stone has so many positive attributes; psychic protector, natural tranquiliser,  excellent to help alleviate mental stress & also to help with anxiety, grief & loss. Also said to help with pain, including headaches, migraine & the healing of injuries & bruises. Place a piece close to your bed to help alleviate insomnia, especially when it is due to an over active mind. 
(As you can see from the pics above, Amethyst is also a great favourite with my cat,Teddi, who jumped into the light box completely of her own volition; she just had to be in on the photo shoot!)
 
All our crystals come with a guide detailing some of their main properties, as detailed above.