What element is primarily responsible for the color changes in sapphire?

The color changes in sapphire are primarily due to the presence of vanadium, which interacts with aluminum oxides in the crystal lattice of sapphire. When vanadium is present in specific concentrations, it can produce a range of color variations, from green to blue and even purple. This is due to the way vanadium affects the light absorption properties of the gemstone.

While other elements like iron, cobalt, and chromium do play roles in coloration—iron can create yellow and brown hues, cobalt is known for producing a vivid blue, and chromium can lend a rich red color—the unique and broad spectrum of colors associated with sapphires is most distinctly influenced by vanadium. The capacity of vanadium to create such alterations in color makes it the primary coloring agent for sapphires, illustrating its significance in establishing the gemstone's diverse palette.