Feature Gems & Gemology, Spring 1984, Vol. 20, No. 1

Pitfalls in Color Grading Diamonds by Machine

Diamonds are normally color graded by comparison with sets of master stones. This method is purely subjective and requires considerable experience. In principle, spectroscopic techniques should enable color grading with high precision by relatively inexperienced operators. In practice, there are at least two major sources of error - luminescence and scattered light - that may make spectroscopically determined color grades unreliable.