Emeralds are green stone, highly valued for its moss green or forest green colour, though as mentioned by the Gemological Institute of America;
“Gem experts differ on the degree of green that makes one stone an emerald and another stone a less-expensive green beryl. Most gemologists, gemological laboratories, and colored stone dealers call a stone green beryl when its color is “too light” for it to be classified as emerald. Even among that group, however, there’s a difference of opinion about what’s considered “too light.””
As mentioned in the quote above, emeralds are the name we give certain colours of Beryl, a family of minerals which comes in a variety of colours, some useful for jewellery purposes, and some too fragile.
Emeralds can be either naturally mined, or made in a lab. Lab grown emeralds tend not to have the ‘jardin’ (the internal inclusions which give it its mossy look), though this does make them less prone to breaking during gem setting.
Emeralds are often cut octagonally, sometimes referred to as ’emerald cut’ due to how common it is. These stones can present a large challenge for setting in metal. Although they are a ‘hard’ stone for a coloured gemstone, they are often riven with internal flaws and inclusions which creates an unstable material prone to breaking.
Although beautiful emeralds should only be cleaned with a soft brush, and a light soap to prevent damage!