You will need a tape measure and a camera to full fill the logging requirements for this Earthcache. Also bring a bottle of water to wet the fossil as this makes it much easier to see it.
The requirements to log this cache are to email me the answers to questions 1, 2 and 3 at my profile:
1.) What is the height of this fossilized Hexagonaria percarinata.
2.) What is the width of this fossilized Hexagonaria percarinata.
3.) What is the diameter of a single polyp in this fossilized Hexagonaria percarinata.
4.) Post with your log a photo of yourself holding your GPS with the breakwater in the background.
This Earthcache will teach you about Hexagonaria percarinata which was a colony coral that lived in the seas that covered Michigan about 350 million years ago during the Devonian period. Then Michigan was near the equator and the seas were tropical in nature. Devonian reefs provided habitat for clams, cephalopods, corals, crinoids, trilobites, fish, and many other life forms. Hexagonaria percarinata is also know as Michigan's state stone, the Petoskey Stone. Petoskey, Michigan is were this fossil was first found. Petoskey Stones are those that have been eroded from the bedrock and have been round by wave action or by the glaciers that covered this area some 10,000 to 12,000 years ago.
Today the fossilized remains of the Hexagonaria percarinata are found in the limestone of the Traverse Group. Near Petoskey they are found the the Gravel Point Formation and in the Alpena area they are found in Alpena Limestone.
The soft living tissue of the coral was called a polyp. At the center of this was the area where food was taken in, or the mouth. This dark spot, has been filled with mud or silt that petrified after falling into the openings. Surrounding the openings were tentacles that were used for gathering food and drawing it into the mouth. The living Hexagonaria percarinata coral thrived on plankton that lived in the warm sea. Calcite, silica and other minerals have replaced the first elements of each cell. Each separate chamber, then, on each Petoskey stone, was a member of a thriving colony of living corals. For that reason the Hexagonaria percarinata is called a colony coral.
A fossil (from Latin fossus, literally "having been dug up") is any rocky remains of a past living organism preserved in Earth's bedrock. The fossilization process typically occurs when a plant or animal's remains sinks to the bottom of a body of water. Sediments then cover the remains protecting it from scavengers and the elements. This slowed the decaying process of the harder body parts. Over time the sediments become rock and water seeped through the rock dissolving the hard body parts. This would leave a hollow cavity that is then filled in by dissolved minerals in the same water that dissolved the hard body parts.
Fossilization is an rare occurrence as the majority of most living organisms are soft and these parts decay quickly. Due to the combined effect of decomposition and simple mathematical chance, fossilization tends to favor organisms with hard body parts, those that were widespread, and those that existed for a long time before going extinct. On the other hand, it is very unusual to find fossils of small, soft bodied, geographically restricted and geologically ephemeral organisms, because of their relative rarity and low likelihood of preservation.
Here is the rock that you are looking for.
The rock you are looking for came from a nearby quarry to provide protection of the shoreline. The mine safety rules restrict the access to mines and quarries unless you have proper safety training. It is about 3' x 3' square and can be easily spotted walking along the rock blocks near the shoreline. This angle favors the best view.