Emerald, the green variety of Beryl, is the most famous and valuable green gemstone. Its beautiful green colour, combined with durability and rarity, make it one of the most expensive gemstones. Deep green is the most desired colour in Emeralds. In general, the paler the colour of an Emerald, the lesser its value. Very pale coloured stones are not called Emeralds but rather “Green Beryl”. They are sometimes heat treated, which causes their colour to turn blue and transform into Aquamarine.
Emerald is the bluish green to green variety of beryl, a mineral species that includes aquamarine.