Is Zakat obligatory on mixed gold or silver not meeting the standard measure?

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Zakat is not obligatory on mixed gold or silver, or that which is mixed with something else, until the measure of the pure gold or silver reaches the established measure (Nisab). This is based on the Prophetic statement, "There is no charity upon less than five Uqiyyah of silver." If one is unsure whether the mixture reaches the Nisab, one has the option to smelt it to determine the exact amount, or to be cautious and pay more to ensure the obligation is discharged certainly. If one chooses the latter and intends to pay from the mixed substance, it is permissible if the adulteration is uniform, such as if every unit contains a known fraction of impurity, as this ensures the payment of one-quarter of a tenth. If the impurity differs or is unknown, payment from the mixed substance is only permissible if one pays an excess amount that guarantees the portion paid as Zakat is pure gold, equivalent to what the pure gold amount would require.