Emerald
Emerald and Esmeraude General Gem Information: Emerald is a type of Beryl, but only the green variety can be called emeralds. Emeralds often contain inclusions or other flaws that may normally be looked at in a negative light- with Emeralds, however, the flaws increase the character of the stone and act as testimony that the gemstone is indeed a natural stone.

Other Properties:
Emerald promotes creativity and perception and can decrease stress and anxiety when your mind is troubled. Emeralds improve memory, help to relieve insomnia, aids the immune system, improves eye sight, reclaims youth, aids in nervous disorders, heals hearing problems and helps to ease child birth.

Notations on Wearing Emerald:
Emerald is the traditional 20th anniversary gemstone. It is the mystical birthstone for January, the Modern and traditional birthstone for the sign Taurus as well as the planetary stone for Taurus. It is the birthstone for the sign Cancer as well. It is also considered a lucky charm stone for Gemini and Cancer.

Emeralds symbolize serenity, good luck with love, wealth, peace of mind and happiness. Ancient Romans associated the stone with Venus.

Links between Emerald and Esmeraude:
Like the stone, Esmeraude is very flawed indeed. However, it certainly seems that Esmeraude wouldn't be truly Esmeraude without her tragic flaws. She is jealous and over-bearing, and aside from attempting to win over Demando she makes no effort to befriend the others of the Black Moon.
Esmeraude could also be compared to Queen Beryl, which comes up in gemology because Emeralds are, after all, a form of Beryl. The characters are similar in the quest for power, desire to be queens, and the fact that they both covet the affection of men who are infatuated or in love with Usagi. (Beryl with Endymion, and Esmeraude with Demando)

References:
Emerald
Find Your Fate- Emerald