Property - gold & silver coins

Respected Sirs, Request to confirm my doubt. While constructing a house in X's site and if luckily X find any property in the form of Gold or Silver coins under the ground during laying of foundation stone. Who will be the owner of that property? Whether the owner/owners can claim it OR will the Govt.'s seizes the property, if YES, whether owner or owners gets any share it. If YES, what could be the percentage. I also want to know under which law it is gourned. Request to clarify the same. Thank you in advance. Shashidhar A