The gemstones never carry their side effects. In fact the gemstones hold the characteristics of their corresponding lord planet and their role in the horoscope of a human kind. Simultaneously, Emerald holds the characteristics of Mercury and it works according to the role of Mercury in the horoscope of a person.
When a person wears a Emerald ring, the power of Mercury gets enhanced. Now it is depending on Mercury as what role it should play as per your Ascendant and Moon zodiac sign. Hence it is necessary to know your Ascendant and Moon zodiac sign before adopting Emerald. The side effects of Emerald / Mercury role are having three type of following views:
Ascendant and Moon zodiac View
The Mool Trikona (the powerful place) of Mercury exists in Virgo where the effect of Mercury is more than Gemini sign. if the Virgo is in 6th 8th or 12th house in your horoscope, then role of Mercury in your life is to create much negative effects in life such as diseases, debt, enmity, hurdles, death, expenses etc. In this case if you adopt Emerald ring then power of Mercury would get enhanced and the problem in life would also increase. Hence Emerald gemstone can not be adopted in Aries, Aquarius and Libra Ascendant / Moon zodiac.
If the Mercury is placed in the 6th 8th or 12th house of your horoscope being the lord of good houses, it also plays the same role as mentioned above. In this condition also Emerald can not be adopted.
If the Mercury is the lord of good houses and also placed in good house then Emerald gemstone can be adopted provided that the power of Mercury in your horoscope is between 0-9 degrees or between 21-30 degrees. But if the Mercury is between 10-20 degrees in horoscope then Mercury is self sufficient to give its full result without any help of Emerald. In this case if any one adopts the Emerald gemstones, the power of Mercury becomes overdose hence balance of other elements in body gets disturbed.