Here's how it works:
* Coral polyps, the tiny animals that build coral reefs, extract calcium and carbonate ions from seawater.
* They then combine these ions to form calcium carbonate, which they secrete as a hard, protective skeleton.
* Over time, these skeletons accumulate, forming the complex and beautiful structures we know as coral reefs.
It's important to note that the hardness of coral is not only due to the calcium carbonate itself but also its crystalline structure. Aragonite, the form of calcium carbonate found in coral, is particularly strong and durable.
