All Citrine is formed when Smoky Quartz or Amethyst is superheated. This change happens at around 800-900 degrees Fahrenheit. Natural Citrine is formed from Geothermal heat in the layer of Earth called the Mantle. The heat of the mantle transforms Amethyst and Smoky Quartz into Citrine within the ground.
Heat-Treated Citrine is formed by humans in lab or factory. After a piece of Amethyst or Smoky Quartz is mined, it is then heated by humans to transform it into Citrine. It is estimated that 90% or more of the "Citrine" on the market today is heat-treated. Natural Citrine is more rare and more expensive.
