Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.047A.

The term ma’din (minerals) is derived from the verb ‘adana (to reside), as in the phrase “‘adana fi almakan,” which means ‘someone resided in some place.’ Allah, the Exalted One, says: “Allah has promised to the believing men and believing women gardens of Eden” [at-Taubah 72] since it is an abode for eternity.

Scholars differ about minerals (ma’din) which are subject to zakah. Ahmad holds that everything dug from the ground, whether created in it or buried by man, and which has a value (such as gold, silver, iron, copper, lead, sapphires, chrysolite, emeralds, turquoise, crystal, agate, kohl (antimony sulfide), arsenic, tar, petroleum, sulphur, zaj) are subject to zakah. He, however, made it a condition that the extracted mineral should attain a nisab either by itself or by its value. Abu Hanifah is of the opinion that zakah is payable on any mineral that can receive an imprint or melt by fire, such as gold, silver, iron, or copper. As for liquids such as tar, or a solid mineral which cannot be melted by fire such as rubies, there is no zakah on them. In the former case, the admissibility of nisab is not a prior condition. Whether large or small in amount, a fifth will be taken as zakah.

Malik and ash-Shaf’i hold that both gold and silver qualify for zakah. Like Ahmad, they insist that the gold should weigh at least twenty mithqal (a weight equal to 4.68 g.) and the silver at least 200 dirhams. They agree (with the Hanafiyyah) that these metals do not require completion of a year to be subjected to zakah, which becomes due anytime it is available. According to the preceding scholars, the amount should be one-fortieth, and its distribution should be like that of the regular zakah. For Abu Hanifah, its distribution is similar to booty (fay’).