A Place for CZ Masters in Diamond Colour Grading

Figure 2. Complete set of GIA graded diamond masters from E through M.

Over the last 20 years and despite recommendations to the contrary,
many gemmologists and appraisers have gravitated to the use of cubic
zirconia (CZ) master stone sets to assist in the colour grading of diamonds.
This investigation revisits with new insight, diamond grading technique and
methodology. It addresses the judicious use of CZ master stone sets to augment diamond masters that are smaller in size and number. Study results support the use of accurately graded, carat-size CZs in reducing the subjectivity of colour grading when only incomplete (every other grade) diamond master sets of small (under 0.4ct ) sizes are available.

Figure 4. CZ Master Sets, colors E-L from Ellin’s Diamonds (top row) and GemOro (bottom row)
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Michael Cowing