The categories in which riba (usury or interest) applies

Question:
The first question: Are riba al-fadl (usury of excess in a like-for-like exchange) and riba al-nasi'ah (usury of deferment) limited to the six categories mentioned in the hadith, or do they apply to everything that is measured or weighed, whether it is food or not, such as iron and copper, and so on?

Answer:
The scholars have reached consensus on the six categories: gold, silver, dates, wheat, barley, and salt. The scholars agreed that riba applies to these six based on the explicit text of the Prophet (peace and blessings be upon him). They differed regarding other items. The majority and most scholars stated that riba applies to other items as well. They treat edible items, such as dates, and grains that are used to make food and are associated with food and benefit from it, in the same way. This is the correct view of the majority: that it is not limited to the six, but that items similar to them are included by analogy. Yes.