What is the ruling on a brick (*ajur*) mixed with impurity?
Chapter on Praying with Impurity and Other Matters
Al-Mughni
Book of Prayer
Primary text
A brick mixed with impurity is impure because fire does not purify it. If the exterior surface of such a brick is washed, the exterior becomes pure because the fire consumed the apparent parts of the impurity, leaving only a trace, which is cleansed by washing, similar to impure ground. The interior of the brick remains impure because water did not reach it.
Supporting text
If one prays on such a washed brick, the ruling is the same as praying on a pure mat spread over impure ground. Furthermore, if a piece of the impure brick breaks off, exposing some of its interior, that exposed part is impure, and prayer upon it is invalid.