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# Why Does a Green Ring Appear Around Hard-Boiled Eggs?
You slice open a hard-boiled egg, expecting a smooth yellow yolk—and there it is.
A faint greenish-gray ring hugging the outside of the yolk.
It doesn’t look appetizing. It raises questions. And for many people, it sparks immediate concern:
*Is the egg spoiled?*
*Did I cook it wrong?*
*Is it safe to eat?*
The short answer: **yes, it’s safe**—and no, it’s not spoiled.
The longer answer is far more interesting. That green ring is the result of a simple chemical reaction, one that reveals a lot about heat, timing, and the delicate science of cooking eggs.
Let’s break it down.
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## The Green Ring Mystery: What Are You Actually Seeing?
The green or gray ring that appears around hard-boiled egg yolks is caused by a compound called **iron sulfide**.
