7.0 on the Mohs scale.
Quartz cystals of different colors often form together to form interesting bi-colored stones. These can be part natural citrine and smoky quartz, or amethyst and colorless quartz, these gemstones are very attractive. Another form of bi-colored quartz is ametrine (amethyst and citrine).
Bi-color quartz is not known to be enhanced.
More information on gemstone enhancements.
Bi-Color Quartz is a member of the Quartz gemstone family.