Septarian forms in "nodules." These concretions are essentially fossilized mud bubbles that began forming during the Cretaceous Period between 50 to 70 million years ago. Its name is derived from the word "septum" meaning partition. As you can see in the photos, these specimens are composed of 3 different minerals, calcite (yellow), aragonite (brown), and limestone (gray). When air pockets are created, they can range from a couple of inches to over a foot in diameter. Often, the calcite and aragonite in these slices are fluorescent under ultraviolet light.
Length: 5.3 in.
Weight: 14.35 oz
Fossil Type: Concretion
Location: Utah, United States
You will receive the septarian slice pictured. Colors may vary based on screen size and resolution.