The World Federation One Stop Fiqh

Ruling 675

If a person cannot find soil, pebbles, a clod of earth, or stone, he must perform tayammum with mud; and if one cannot find any mud, he must perform tayammum on top of a carpet, clothing, or similar thing that has gathered dust or on which dust has settled but not to the extent that it can commonly be considered to be soil. If none of these can be found, the recommended precaution is that one should perform prayers without performing tayammum; however, it is obligatory on him to make them up afterwards.