Inktober 2022 Day 4- Scallop

Inktober sketch. Day 4. Scallop. A few days ago I visited the Skegness (UK) seaside and picked up a couple of shells, including this piece that I've tried to illustrate. The shape reminds me of flint or slate but it has what appear to be shells imbedded in it. I would really like to know how it was formed? could it be a rock that has chipped off a cliff? is it a result of lighting striking he sand giving it a glass like quality, or the result of an Alien craft landing on the beach and creating this. Maybe a rock from Space. Could it be man made? It's nice trying to come up with theories, but nice to know the real reason for its existence.
Enjoy.
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