Witch quartz? I love them all, but again, there all different.
Zodiac: Aquarius, Pisces.
Amethyst is great from calming yourself. Keep it near you or next to you to promote calmness, Also keeping it under/in your pillow and it will ward off bad dreams and nightmares.
Amethyst is said to lose it's color when the holder/wearer is Ill. It will turn a slightly paler purple than it is, if you don't have an eye for colors you might not notice, as sometimes the color change isn't very drastic.
Amethyst is said to help the healing of internal organs and illnesses. When feeling a little sad, a little amethyst will keep you came and controlled.
All in all it is a very spiritual stone and is a must have for ,e anyway, because it will also help to keep divination tools cleansed and powered. It will also help you to give more insightful readings.
Hope i helped :D