Emerald is a very calm and soft gemstone. Due to its softness the side effects of emerald does not be intense. If Emerald is not suitable you will lose the patience. You will hurry in everything. You will not use your head and you will become careless to others.
The problems related to teeth will start arising. In routine conversation you will speak on useless and unnecessary points. You will not choose right words right time. In speaking you will hesitate or you will become over confident. In spite of not suitable if you do not remove this gemstone you might be start suffering from asthma or breathing problem. Long term use of such gemstone will give you that kind of effects.
Other than this you will have problems related to Mercury placement in your horoscope. For example if the Mercury is situated in 8th house you will have infection in your stomach, if your Mercury is in 12th house you will not able to sleep properly. If your Mercury is situated in 6th house you will be surrounded by enemies in few days.
The same effect will be of any kind of substitute of Emerald like onyx, green Aget, Green Zircon, Turquoise etc.