What is true about the use of masterstones in grading?

• A. Masterstones and the diamond to be graded must be clean for best results
• B. Cleaning is optional
• C. Only the diamond must be clean
• D. Only the masterstones must be clean

Answer: (A)

When grading with masterstones, having both the masterstones and the diamond clean is essential because dirt, oils, or fingerprints can alter how light interacts with the surfaces and how colors or inclusions are perceived. Masterstones serve as standardized references, so any contamination on either the stone or the diamond can change the appearance of color, tone, or clarity, leading to an inaccurate comparison and grading result. Clean surfaces ensure that the light seen by the eye reflects the true properties of the diamond and the reference stones, providing consistent, reliable comparisons. If either side is dirty, the assessment can be biased by surface residue rather than by the actual gem characteristics. That’s why cleaning both the masterstones and the diamond is required for best results.