Orange tourmaline is one of the rarest color varieties of tourmaline gemstones. Its vibrant reddish-orange to orange-yellow hues are caused by heating pink or red tourmaline crystals to very high temperatures.
This heat treatment process is what makes orange tourmaline so unique and scarce compared to other tourmaline colors that occur naturally without treatment.
The heating, often done in an oxidizing atmosphere, causes changes to the valence state of the mineral's iron and manganese components. This alters the way the tourmaline absorbs and reflects light wavelengths, producing the prized orange to orange-yellow colors.
