A piece of coral with calcite crystals in it

It looks like it’s modern and not a fossil

coral. And probably a modern day one, so not a fossil.

The ability to form a calcium carbonate skeleton represents an evolutionary innovation of major importance that dates back to the onset of the Phanerozoic (ca. 540 Ma) (1). Since that time, multiple groups of marine metazoans became highly efficient reef builders, creating the structural foundation for the richest and most biodiverse ecosystems in…[Read more]

Many marine organisms, including corals, build skeletons from calcium carbonate — in the form of calcite or aragonite. The current composition of seawater favors the formation of aragonite — but soft corals have a specific protein that allows them to form calcite skeletons instead.