The main color cause in pink-to-red diamonds is deformation-caused selective absorption.

• A. Radiation-induced color
• B. Deformation-caused selective absorption
• C. Nitrogen-related defects
• D. Surface defects

Answer: (B)

The color in pink-to-red diamonds comes from deformation-caused selective absorption. When the crystal lattice is distorted by plastic deformation or internal stress, it creates specific color centers that alter how light is absorbed. This changes the spectrum that is transmitted, removing certain wavelengths and leaving pink to red hues. This mechanism is distinct from radiation-induced color, which relies on light exposure creating color centers, or from impurities like nitrogen, which typically produce yellow or brown tones. Surface defects also don’t account for the saturated pink to red color seen in these stones. So, the deformation-induced lattice changes are the primary driver of pink-to-red color.