Quartz is the second most common mineral in the Earth’s continental crust. It is mainly composed of Silica or Silica based minerals. Although Quartz is known by a variety of names, the most important distinction between types of Quartz is that of macro-crystalline, individual crystals visible to the unaided eye, and micro-crystalline, where aggregates of crystals are only visible under high magnification. There are many forms of Quartz including Chalcedony, Amethyst, Citrine, and Carnelian which are results of mineral impurities or heat treatments.
Citrine is any Quartz Crystal or cluster that is yellow or orange in color. Most Citrine, usually begins as Amethyst which becomes yellow due to heat treatments. True Citrine is often rarer but is hard to distinguish from the heat treated variety. It is widely distributed as a mineral, but fine, clear specimens that are suitable for cutting as ornamental stones.