What happens to dhun when treated?

When dhun, also known as dhunei or a type of corundum, is treated, it typically undergoes a process that enhances its color, often resulting in a blue hue. This treatment usually involves processes like heat treatment or diffusion, where various elements are introduced to alter the stone's appearance. In the case of dhun, the treatment enhances its natural properties, leading to a more vibrant and appealing blue color, which is highly sought after in the gemstones market.

Other options describe potential transformations that dhun does not experience when treated. For instance, becoming colorless or opaque does not align with the expected outcomes of enhancing its color properties, and gaining a red hue is not a typical result of the treatments applied to dhun. Thus, the conversion to blue is the accurate reflection of the changes that occur during its treatment.