How should continuous extraction efforts be accounted for when calculating the Nisab of minerals?
Chapter on Zakat on Gold and Silver
Al-Mughni
Book of Zakat
Primary text
The extraction required to complete the Nisab must be continuous, whether performed all at once or in successive efforts. Work must not be abandoned intentionally between extractions. If an amount less than the Nisab is extracted, the work is abandoned, and subsequently, another amount less than the Nisab is extracted, no Zakah is due even if the total reaches the Nisab. If one extraction reaches the Nisab while the other does not, Zakah is due only on the amount that reached the Nisab, and the remainder is calculated proportionally.
Supporting text
Abandoning work temporarily due to nightfall, rest, illness, repairing tools, or the flight of slaves does not terminate the continuity of the effort; the amounts extracted in these separate instances must be combined to fulfill the Nisab. Similarly, if soil containing no value is extracted between mineral-bearing extractions, this interim matter does not interrupt the continuity.