Assertion: coral's skeleton | /r/MadeOf | calcium carbonate
Facets:
Source sentences:
text: Order Scleractinia, Stony Corals: Stony or reef-building corals form a skeleton made of calcium carbonate under the polyps to create the hard structure that most people recognize as coral.
text: The polyp uses calcium and carbonate ions from seawater to build itself a hard, cup-shaped skeleton made of calcium carbonate (limestone).
text: The corals in effect build limestone because their skeletons are made of calcium carbonate.
text: The skeleton of Elkhorn coral is made of calcium carbonate.