Congratulations, you've discovered an Ametrine Gemstone!!
Ametrine, also known as trystine, is a naturally occuring variety of quartz. It is a combination of amethyst and citrine and displays zones of purple, yellow, and orange. Because the zoning is natural, no two ametrine gems will be the same.
Ametrine, by legend, was introduced to Europe by a conquistador's gifts to a Spanish queen. He received a mine in Bolivia as a dowry when he married a princess from a native tribe.
Ametrine is mined in Bolivia, and that is believed to be the only source of the gem.