What am I?

Cover the clues so you can only see number one. How many clues do you need before you know the answer?

1. I was picked up with by a man called Brian Scanlon. He found others like me too.
2. I came from Back Beach.
3. I have tiny bits of shell inside me.
4. I could be the result of burrowing marine worms or of bubbles escaping to the surface through the sand.
5. Some people collect shells but I am just as interesting.

Answer in next week's TreasureLink.