Milky and Cloudy Diamonds Explained
A hazy, washed-out look that a certificate's clarity grade alone won't warn you about — what causes it and how to check before you buy.
Short answer: milky or cloudy diamonds have a hazy, washed-out, less transparent look that isn't always predicted by their stated clarity grade — this is one of the clearest cases where you genuinely need to see the actual stone, not just its certificate numbers.
What causes the haze
The most common cause is a dense concentration of sub-microscopic "cloud" inclusions — clusters of pinpoint crystals too small and numerous to individually affect the clarity grade in the usual way, but collectively scattering light enough to reduce transparency and brilliance. Strong fluorescence (see our fluorescence guide) can also contribute to a chalky, hazy look in some stones, particularly under UV-rich daylight.
Why the clarity grade doesn't reliably catch this
Clarity grading assesses the size, number, position and visibility of individual inclusions — it isn't designed to specifically capture the cumulative haziness that dense clouds of very small inclusions can cause. A diamond can carry a VS2 or even VVS clarity grade and still look noticeably milky, because the grading system and the "does it look cloudy" question are measuring genuinely different things.
How to check before buying
View the stone in daylight if buying in person; if buying online, insist on video specifically, since a milky or cloudy effect is often much harder to spot in a single still photo than in the stone moving under changing light. This matters most in the VS2–SI1 clarity range, where cloud inclusions are common enough to be a real risk but not automatically flagged by the grade alone.
What it does to price
Milky diamonds typically trade at a real discount versus a comparable clean stone of the same certificate grade — commonly cited in trade pricing as somewhere in the region of 10–30% below an equivalent clean stone, reflecting the genuine gap between what the certificate states and what the stone actually looks like.
Related reading
Source: causes and pricing impact of milky/cloudy diamonds per current trade-jeweller education content (Diamonds.pro, Frank Darling, Beyond4Cs).
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