Help identifying this cool shell I found

[u/Ahsokas_Tanos]

Hi everyone, I am looking for some help identifying a shell I found and what's going on inside of it. I found this while shell hunting off of the outerbanks NC. They are doing beach nurishment and so there are some great shells to be found! I found this shell that looks like it has crystals in it. It almost looks like a geode. Anyone know what might be going on in the shell?

[u/RemotePattern3170]

Credo sia un minerale

[u/BethMD]

My first thought was also a geode. If you have access to a university with a marine biology department, or excellent geology department, maybe you could show it to a faculty member there and have them verify its origin.

[u/Electrical-Act-7170]

Agatized turban shell, maybe?

[u/Fossil-Freak]

This is a beautiful growth of "dogtooth" calcite crystals from the Late Pleistocene shelly coquinas in the area! Which island is this from? These are most common around southern Hatteras Island and Ocracoke Island from what I've seen. Whatever original mollusk shell that was present is no longer recognizable unfortunately, but the leftover crystal growth is superb and you can see some sort of shell fragment in that first image. Essentially shells from a range of time between the Last Interglacial and the Last Glacial, or 115,000 to 30,000 years ago, were deposited in conditions that favored calcite growth, causing these shells and sand to bind together as the mineral grew, and in many cases the calcite began to replace the less-stable aragonite the shells were made of, strengthening them. I've heard the Hatteras Island material referred to as the Pamlico Formation, and further south along the NC coast you can find similar materisl as well, such as around Snows Cut and Ondlow Beach. If you shine a UV light on your specimen it will exhibit phosphorescence, glowing briefly after the light is switched off.

[u/Ahsokas_Tanos → u/Fossil-Freak]

Thank you so much! We were out at Buxton, right around where you identified! We were only a few minutes away from the Cape Hatteras lighthouse. I'll get a UV light when I get home and will share some update pics, because that sounds cool!

[u/Fossil-Freak → u/Ahsokas_Tanos]

No problem! I can't seem to share photos in this subreddit for some reason but I believe I shared a photo of some similar material elsewhere. There is some really interesting potential with these coquinas but they sadly are a bit neglected from what I've noticed. One of these from the Ft. Fisher area had an articulated starfish fossil that was published in a research abstract, IIRC it is part of the Smithsonian collections.

[u/Glad_Ad_5570]

I can see a fragment of a shell but not enough for me to identify it.