Is it permissible to sell a goldsmith's or mineral earth for something of its own kind?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
The sale of goldsmith's earth or mineral earth for something of its own kind is impermissible. This is because it constitutes a prohibited transaction of Riba (usury) involving the exchange of like for like where the measure of equality between them is unknown. Such a transaction is void, similar to selling a measure of grain for another measure of grain. This view is supported by the established principles of Islamic jurisprudence concerning the exchange of commodities subject to Riba.
Supporting text
A dissenting view held by Ibn Abi Musa in Al-Irshad permits this exchange. This view is also attributed to Malik, Al-Hasan, Al-Nakha'i, Rabi'ah, Al-Layth, and others. They stipulate that if the earth is mixed or uncertain, it must be sold for a commodity (*'ard*) and not for specie (*'ayn*) or silver (*waraq*), as this involves selling for something exempt from Riba, making the transaction valid, similar to buying a garment for a Dinar and a Dirham.