As read in my favorite English newspaper in France, The Connexion, there are specific rules over ownership of hidden or buried treasures. Basically you are entitled to 1/2 of it with the owner (if it's not on your property). This article was prompted by a discovery of 16 bars and 600 coins builders found while working on a project. The value is €900,000.
Not only is this good information, but I doubt we'd read these kinds of articles in a newspaper in the United States. So much of the USA is already dug up, stories of buried treasure I think must be at least 100 years old.