Citrine is a crystal that comes in the colors yellow, yellow-brown, orange, dark orange, and reddish brown.
Natural citrine is rare. It is naturally found in Madagascar, Brazil, Russia, and in the Alps in Austria. However, most citrine is made by heat treating smokey quartz and purple amethyst.
This process would make Citrine ruled by Mercury since it was heat treated naturally or by man. It is an alchemical process which took place.