The Ruling on Tayammum on Hard Ground

Question:
If there are stones or hard ground on the surface of the earth, does one perform tayammum?

Answer:
One performs tayammum, applying the dust to oneself, as much as is possible for him if he finds nothing else.
Q: What if there is no sand or anything else?
A: What is on the surface of the earth is the dust (sa'id). If soil is available, praise be to Allah; otherwise, even if it is on a mountain.
Q: What about one who lacks the two purifiers, does he pray without...?
A: It may be said so, but the generality of the text requires that he do what is stated: [Al-Nisa: 43]. He wipes with what he has of mountain rock, plaster, sand, or otherwise, and the meaning is the same... However, this is the most cautious course to avoid the difference of opinion; because a group of scholars said: one strikes the earth absolutely, even if it is mountainous. The important thing is that his striking of it does not contradict the statement of the one who said that he lacks the purifiers; because the one who lacks the purifiers is excused, and this person is excused if he strikes it; because he feared Allah as much as he was able.