5 Facts about Fossil Coral You Didn’t Know

1.Fossil Corals Are Not Coral Reefs

Believe it or not, fossil corals are actually natural stones that formed when ancient corals were replaced by agate. Agates are semi-precious gemstones typically formed in sedimentary rock cavities, and are composed of varying types of minerals leading to its unique coloring and pattern.

Millions of years ago, coral lived in warm shallow water. Over time, as plates below the ocean floor shifted, the coral became buried under layers and layers of sediments. As the temperature and pressure changed, the coral eventually fossilized and turned into rock.  

2.      Fossil Corals Are Not Endangered

Unlike the protected (living) coral reefs we know of today, fossil corals are not endangered as they are considered rocks (the official name is agatized coral). Originally from an extinct form of rugose and tabulate coral species, their hard skeletons fossilized when they were saturated with silica rich water bubbling from limestone. 

3.      It’s the State Rock of Florida and Michigan  

Found all over the world, fossil corals are particularly abundant in Florida and Michigan . The official state rock of Florida (as agatized coral) and Michigan (as Petoskey stone), it’s known for its colorful hues and floral almost lace like patterns. Many of Florida’s coral fossils are found in Tampa Bay, near Ballas Point, while Petoskey stones are found along the shores of the Great Lakes.

Other areas that are famous for their fossil coral include Indonesia, where entire heads of corals have been found completely preserved and undamaged. In Le Roy, New York, a 100 acre fossil coral reef known as Bradbury Quarry was also discovered and declared a National Natural Landmark in 1967.

4.      The Oldest Fossil Coral is 450 Million Years Old

The oldest fossil corals are over 450 million years old and are from the Ordovician period. During this time, marine animals like algae, coral, primitive jawless fish and gastropods ruled the earth. Most coral found today can be anywhere from 100,000 to 25 million years old, though there have been many older specimens found from the Silurian age (390 million years ago).

5.      Makes Great Calcium Supplements and Jewelry

Found in abundance in quarry mines, fossil coral is often ground up and turned into health supplements, cement, paint additive and even tooth paste filler. However, the most ornate and unique specimens can be polished and made into amazingly intricate pieces of luxury jewelry for both men and women. Structurally tough (it measures around 7 on the Mohs scale; steel is 5.5), fossil coral products are immensely popular with rock collectors, budding paleontologists and anyone who loves to give and receive a unique gift.

Bio: Since 1997 William Henry has been a luxury brand dedicated to bringing ground breaking and functional designs in the world of men’s jewelry. The winner of the 2013 JCK Jeweler’s Choice Awards, its devotion to procuring exotic and state of the art material, such as fossil coral and dinosaur bone, has made it a unique voice in the industry. For more information, please visit them at