Ametrine is a completely natural though rare combination of Amethyst and Citrine. The colour depends on the heat fluctuations of the Earth during formation. Lower temperature results in Amethyst forming and when it rises Citrine will form from the Amethyst.
You can sometimes find crystals containing both stones in one piece - like this pendant!
This stunning pendant is 3.5cm in length and has a beautiful teardrop shaped Ametrine.