It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: The blood of one who is killed by an animal is wasted; the blood of one who dies by falling into a well is wasted; the blood of one who dies in a mine is also wasted; and for the buried treasure (found by someone), one-fifth (khums) is obligatory.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 9005