Ruling 1816 — The One-Fifth Tax (Khums)

The niṣāb for mined products is fifteen common (ṣayrafī) mithqāls[1] of coined gold, i.e. if the value of something that is extracted from a mine reaches fifteen common mithqāls of coined gold after deducting the costs for extracting it, then the subsequent expenses – such as the costs for purifying it – are subtracted and khums must be paid on the remainder.