What effect does heat-treating have on Mong Hsu rubies?

Heat-treating Mong Hsu rubies plays a crucial role in improving their overall appearance, particularly by minimizing or eliminating dark centers or cores that can detract from the stone's visual appeal. This process involves heating the rubies to high temperatures, which not only alters the internal structure but also allows the color to become more uniform.

When rubies are mined, they often exhibit zoning or areas of inconsistent color, including darker cores that can make the stone appear less vivid. The heat treatment helps to break down the absorbing elements in the crystal structure, which can reduce these darker areas and lead to a more desirable, brighter ruby.

While it is true that heat treatment can enhance color (which is sometimes considered a side effect of the process), the specific focus in the case of Mong Hsu rubies is on addressing the existence of dark centers, making option B the most appropriate choice.