Not if you live in England & Wales. The Treasure Act of 1996 defines what must be done if you believe you have discovered "treasure."
Here's a link that gives info on it if anyone is interested:
If someone discovers what can be deemed as "treasure," and they don't report it, they can be fined up to $5,000 pounds ($10,306.50 US). They take their heritage very seriously in England.
Naturally, in GB as in all socialist countries everything belongs to the state.