Emerald; May's birthstone
Emerald, a green variety of Beryl (falls under the same group as Aquamarine and Morganite), can come in different shades of green, ranging from light yellow-green to bluish green to pure green. Almost all emeralds have inclusions that are visible to the unaided eye. Eye clean emeralds are extremely rare, hence if you ever come across one, consider yourself lucky.
Emerald is considered to be a royal gemstone, favored by queens, kings, pharoahs and conquerers. It was the most sought after and expensive gemstone in the middle ages, being the symbol of faith, heart protection, courage, love, joy, abundance, wealth and prosperity.
Today, Emerald is still considered a great stone for attracting love, boosting self esteem and restoring confidence. It is also known for its calming effects which promote creativity and focus.
Do note that because of surface reaching fractures (common in emeralds), more that 90% of emeralds are fracture filled. This results in increased durability and enhances the color. Careful care is required if you own jewelry set with emerald. Do not use ultrasonic cleaner or steam to clean your gem.
A best way to clean emeralds (and any other gemstone if you're unsure) would be using a soft bristle toothbrush and warm mild soapy water.