The oiling of flawed emeralds as a routine proceedure is an obvious example of such treatment. The oil enters the gem through internal cracks which break the surface of the stone. After a period of time the oil drys and the flaws are again visible. A clean and auspicious emerald cannot be oiled because it has no internal cracks breaking the surface. There is no way for oil or anything to enter into a fine, intact non-cracked single unit gem crystal of auspicious health.
Flawed gems are far less beautiful and can be a source of misfortune.
Most people will not buy torn clothes or a new car with obvious defects. Almost no one uses cracked eyeglasses. A good way to think about gem clarity is to mentally compare the location and seriousness of flaws in a gem to similar defects in your own body. If there are minimal flaws in either a gem or your body, there is life and power. But if the defects are too severe, there is neither life nor power.