Abstract:

Rubies, as significant gemstone materials, have garnered extensive attention for their color characteristics. Exploring the relationship between the color of rubies and their chemical composition is essential for foundational research in gemology and for a deeper understanding of mineral formation mechanisms. This study analyzed 30 faceted rubies (including vivid red, slight purple, and slight pink hues) using UV-Visible spectroscopy, X-ray fluorescence spectroscopy, and color characteristic analysis. The findings indicate that the color of rubies is closely related to their chemical composition, primarily controlled by the Cr content, along with influences from elements such as Fe, V, and Ti. The absorption due to the d-d electron transition (⁴A₂→⁴T₂) of Cr³⁺is most prominent in rubies with a slight purple hue, whereas the absorption related to the d-d electron transition (⁴A₂→⁴T₁) and the fluorescence emission peak of Cr³⁺ is most significant in rubies with a slight pink hue. Additionally, the absorption intensities at 412 nm and 548 nm in the UV-Visible spectrum effectively indicate the intensity of the purple tone in rubies; higher absorption intensities at these wavelengths correlate with a more pronounced purple hue. The 412 nm wavelength serves as an indicator wavelength for the color parameters L and b of rubies, demonstrating a significant negative correlation with the brightness parameter L and a significant positive correlation with the b value. This finding provides a new perspective for the quantitative analysis of ruby color characteristics.

Key words: ruby, chromogenic origin, color, UV-Visible spectroscopy, X-ray fluorescence spectroscopy