Which instrument is commonly used to determine color origin in diamonds?

• A. X-ray diffraction spectrometer
• B. Scanning electron microscope
• C. Raman spectrometer
• D. UV-VIS-NIR spectrometer

Answer: (D)

The main idea is that diamond color is revealed by how the stone absorbs light across a range of wavelengths. A UV-VIS-NIR spectrometer shines light through or measures transmitted light and records how much is absorbed at each wavelength. The resulting absorption spectrum shows specific bands or features that correspond to particular defects or impurities in the crystal, which are the actual color causes. By comparing these features to known signatures—for example, nitrogen-related centers that tend to produce yellow/brown tones, boron that leads to blue, or irradiation-induced defects that create greens and pinks—you can identify the color origin of the diamond.

Other instruments don’t provide this direct link between absorption features and color origins. X-ray diffraction looks at crystal structure, not which wavelengths are absorbed to produce color. A scanning electron microscope examines surface morphology and can do microanalysis for composition, but it isn’t used to map the optical absorption across the spectrum. Raman spectroscopy reveals vibrational modes of the lattice, which helps with identity and structure but not the specific absorption bands tied to color centers. The UV-VIS-NIR spectrometer is the standard tool for connecting observed color to the underlying causes in the diamond’s optical absorption.