Treasure – Trove
1: A treasure trove is a property which is hidden underground, or in a tree or a mountain or a wall, and someone finds it out. It should be in such form that it can be called a treasure-trove.
2: If a person finds a treasure-trove in a land which does not belong to anyone, he can appropriate it, but he must pay Khums on it.
3: The taxable limit of a treasure-trove is 105 mithqals of coined silver or 15 mithqals of coined gold. It means that any thing found in the treasure should be equal to the above mentioned value of either of the metals before it becomes liable for Khums.
4: If two persons find a treasure-trove whose total value reaches 105 mithqals of silver or 15 mithqals of gold, they would not pay Khums on it if the share of each one of them may not come to the minimum taxable limit.
5: If a person purchases an animal, and finds some valuables in its belly, it is necessary for him to inform the seller or the previous owner about it, provided that he has a strong feeling that it could belong to either of them, and that they owned it together with what was in the belly of the animal.
But if he finds that it does not belong to either, as an obligatory precaution, he will pay Khums on it, even if its value is less than the minimum limit. This rule applies to fish and its like, if they were looked after in a special place like fish farm, and someone supervised its feeding. But if the fish was caught from an open sea or a river, then it is not at all necessary to inform anyone
These laws are according to Aayatullah Sistani's Fataawa.