Emerald Vs Green Beryl

Emerald can own its green colouration to Chromium and iron, but the question was raised when vanadium coloured green beryl was found in Brazil... Up to this point, it was common that 'emerald is the green variety of beryl, it is coloured by chromium". Most emeralds are coloured in fact by iron and chromium, some other stones can also be colored by vanadium. 

For most gemological laboratories the standard is that if a green stone from the beryl family shows some chromium spectrum and present a chromium percentage higher than 0,1% then it can be called emerald. 
If not it is green beryl... 

This 0,1% "standard" is coming from a Kurt Nassau proposal in order to solve the problem opposing Colombian emerald dealers and brazil or African dealers: As most of the Colombian emeralds which are the traditional emeralds owns their colour to chromium and iron. The new emeralds from brazil were vanadium rich. The Colombian dealer lobby was the stronger, this proposal has been globally accepted. 

You can so have a very saturated green beryl coloured by vanadium but without the 0,1% of chromium and a weak green emerald that can be called emerald despite its weak green color because its host 0,1% of chromium... 

But anyway on the internet an emerald sells better than green beryl... so many people try to be ignorant in order to make better sales and margins. In gem business, it is sad to say but the greed of some is very well completed with the greed and the greater ignorance of the others!