No it does not. Some people prefer it that way but I think that is a very personal choice and there are no rules. You can most defintely use an amethyst ball for divination/scrying.
I have an amethyst ball and I find it very healing and helpful and INSIGHTFUL!!!
I have an obsidian 'crystal' ball, and one crystal one with many inclusions and 'defects'. i don't scry with them; rather I sit with them in hand and meditate. ( Supposedly, Ho Tei (sp?) is holding a white or clear ball in one hand and a dark one in the other)
Has anyone been practicing the more traditional form of scrying??? If so, what experiences have you had with it??? As I mentioned before, I have a smokey quartz crystal ball but have only "acquainted" myself to it and its energies.