Ametrine
This rather exotic stone, typically has two colors in the same gem. Purple (amethyst) and yellow (citrine) come together to form this unique stone.
Ametrine is found in mainly Bolivia. This quartz gem has a hardness of 7 and often is formed in large trigonal crystals or in clusters such as those found in geodes. A unique gemstone, Ametrine (SiO2) has the same chemical makeup as amethyst, citrine, rose quartz, and tiger-eye.