1. Natural Amethyst
2. Howlite (Dyed Turquoise)
3. Carnelien/Onyx/Amber- Check if weight is extremely light then it is amber
4. Black onyx
Diffcult to judge without seeing picture.
I am 100% sure that this is brazilian amethyst.
Black star sapphire it is,
Use a white light torch and when you face light on top of the stone then you will see a vertical line and when you move stone slowly from right to left or left to right then that line moves also.