What is the main color-causing mechanism in pink-to-red diamonds?

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

Answer: (D)

The color in pink-to-red diamonds mainly comes from deformation-caused selective absorption. When the crystal lattice is distorted by plastic deformation, strain fields around defects alter the electronic structure of the carbon lattice. This changes how certain wavelengths of light are absorbed, typically absorbing more of the blue-green end and leaving red to pink hues visible. The result is a pink to red color that is intrinsic to the crystal’s structure rather than due to simple impurities.

This differs from radiation-induced colors (which typically produce greens or yellows) and nitrogen-related colors (which yield yellow to brown tints). Surface polishing marks don’t create a stable color either.