What causes the pink color of corundum?

The pink color of corundum, which is commonly known as ruby when it displays this hue, is primarily caused by the presence of chromium in its crystal structure. When chromium atoms replace aluminum atoms in the corundum, they can influence the absorption of specific wavelengths of light, leading to the beautiful pink coloration observed in the stone.

Chromium's involvement in producing pigmentation in corundum is well-studied; it absorbs light in the blue and yellow regions of the spectrum, allowing the pink shades to be reflected. The exact shade can vary depending on the concentration of chromium and the presence of other trace elements.

Other elements such as vanadium, manganese, and iron can also influence the color of corundum, but they do not produce the same distinct pink hue associated with chromium. Vanadium can create bluish colors, manganese may contribute to orange or purple hues, and iron can contribute to yellow or brown tones. None of these elements generate a pure pink color like chromium does.

Therefore, understanding the role of chromium in the colorization of corundum is essential for identifying and appreciating the variations of ruby and other pink sapphires.