What role do transition elements play in gemstones?

Transition elements play a significant role in the coloration of gemstones due to their ability to selectively absorb certain wavelengths of visible light. This absorption leads to the manifestation of different colors depending on the specific transition elements present within the gemstone's crystal structure.

For instance, in stones like sapphire and ruby, the presence of chromium and iron can lead to distinctive red and blue colors because these elements absorb light at particular wavelengths while allowing others to pass through. The thickness of the stone and its lighting conditions can further influence the appearance of color, but the fundamental mechanism is rooted in the interaction of light with the electronic structure of the transition elements.

This characteristic distinguishes transition elements from other elements in gemstones, as their d-orbitals allow for varying degrees of electron excitation and thus varied absorption spectra, ultimately resulting in the vibrant colors that make colored stones so desirable.