Fossilised Coral Facts and Photos

What is Fossilised Coral?

Fossilised coral is the result of fossilised coral colonies which date back approximately three hundred and fifty million years.

Stones can be found in several locations worldwide. Some of the finest material comes from the shores of Lake Michigan in the USA and from Indonesia.

Fossilised coral is an extinct species of coral that lived in the sea millions of years ago. Hexagonaria, as it's officially known, is one of the most common varieties.

The class known as hexagonaria percarinata is found close to Little Traverse Bay off Lake Michigan.

Widely used for decorative purposes, fossilised coral from the USA is known as Petoskey Stone. The stone and city of Petoskey, which lies on the southeast shore of Little Traverse Bay, are named after a 19th-century Indigenous American chief. 'Petoskey' is an anglicised version of his name which was Chief Pet-O-Sega or Petosegay.

How Fossilised Coral Formed

Fossilised coral formed when sections of the ancient coral were gradually replaced by natural minerals, including calcite and silica.

The corals had been growing in the oceans for almost five hundred million years. Many thrived in warm, shallow waters.

Over time, they became buried under sediments as the land surface moved and oceans rose and fell. Temperature and pressure from compaction caused deposits to slowly turn to stone, a process known as petrifaction.

Three hundred and fifty million years ago, the land that makes up Michigan was situated near the equator. At that point in the Devonian Period, a large shallow sea covered a significant part of the United States.

Much of Michigan was home to a large coral reef populated by various species of fish, trilobite and cephalopods. Although fossils of all these creatures have been found, the most famous are the corals themselves.

Fossilised coral was a mid-sized coral renowned for its honeycombed appearance. Individual coral creatures known as polyps secreted a limey substance which created a corallite skeleton. When the skeletons combined, they formed large coral reefs composed of millions of individual creatures. Over time, parts of the reefs fossilised.

Article Pictures

The first picture in our article is courtesy of interwebsafari, the second is courtesy of Empirebluff. Both are clickable and redirect to the original image on Reddit.