What substances qualify as minerals subject to Zakat?
Chapter on Zakat on Gold and Silver
Al-Mughni
Book of Zakat
Primary text
Every substance extracted from the earth that has value and is not naturally part of the earth's composition is subject to Zakat. This includes solid substances like iron and gemstones, and flowing substances like bitumen, naphtha, and sulfur.
Supporting text
Abu Hanifa, in one narration, limits Zakat to malleable substances such as lead, iron, and copper, excluding others.