Diamond Windowing and Extinction Explained
Two different ways a poorly cut diamond fails to sparkle — windowing lets light pass straight through, extinction traps it without returning it.
Short answer: windowing means you can see through part of the stone like glass; extinction means dark, dead-looking patches where light enters but never bounces back out. Both point to the same underlying cause — proportions cut for weight retention rather than light performance.
Windowing
Windowing happens when a diamond's pavilion (the lower half) is cut too shallow, so light entering the top passes straight through the bottom and out the other side instead of reflecting back to the viewer's eye. The visual effect is a pale, washed-out, semi-transparent patch — you can sometimes see straight through to whatever's underneath the stone, which is where the "window" name comes from. It's most visible face-up, in a well-lit environment, and it's one of the clearest visual signs of a diamond cut to preserve carat weight rather than for brilliance.
Extinction
Extinction is close to the opposite visual problem with a related cause: dark, dead patches where light that enters the stone gets trapped and reflected internally in a way that never makes it back out to the eye. Where windowing looks pale and transparent, extinction looks dark and lifeless — both reduce a stone's overall sparkle, and a poorly proportioned diamond can show both problems simultaneously in different areas of the same stone.
Why this happens
Cutters sometimes prioritise retaining rough diamond weight over ideal proportions, since a heavier finished stone sells for more per carat even at a lower cut grade. A shallow pavilion (windowing) or an overly deep one (a common cause of extinction) can both be the result of that trade-off.
How to check for it
Look at real photos or video of the specific stone, face-up, in ordinary lighting — not just the certificate's numeric proportions. A cut grade of "Excellent" or "Very Good" from a major lab (see our cert lab guide) is a strong indicator against both problems, but isn't an absolute guarantee for every shape — fancy shapes without a standardised cut-grade scale (most shapes besides round) benefit especially from an actual visual check before you buy.
Related reading
Source: windowing/extinction mechanisms per current trade-jeweller education content (LooseGrownDiamond, 4CGrownDiamond, PriceScope).
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Compare real stones before you commit
Use Chaos to understand certificates, pricing, availability and dealer supply before asking for a specific stone.