1. If grass becomes najis with urine or some other najasat how do we make it tahir considering that according to Ayatullah Sistani sun cannot make the grass tahir?
2. Just to confirm if a person does not have a turbah they can prostrate on stone such as aqiq right? Is it fine if the stone is in a ring?

1. You can wash it with water
2. Yes it can be used, provided there is stability during sajda