Khan doesn't grin, even if Berserker had made an even greater mistake. There was no distinction when it came to sand. The stuff he carried had no key difference to the kind you'd find at a beach, or that filled deserts across the world. All that mattered was that it was in range.
The sandstorm Berserker had created grinds to a halt. For a moment there it hangs there in a suspended mirage, various grains halting even as they score minute gouges in his mask and clothing. That was what the clothing was there for, after all. Then it lurches in the other direction, swirling in directed blasts up Berserker's arms and back.