Emerald is May's birthstone
Emeralds are sometimes found inside shale, a rock with a very fine grain. Like aquamarines, they're a form of the mineral beryl. These gems are a light to deep green. What a fitting color to represent May, when spring is in the air and new growth is beginning.
An emerald can melt a snake's eyes! Well, that's what people used to believe. They also thought these gems would relax your eyes if you looked through them. Other beliefs: Emeralds stopped bleeding, cured fevers, and they supposedly held powers for predicting the future.