I am currently the Digital Coach for the City of London and the West, within the London and Midlands Region. My role in a nutshell is to coach our leaders on sustainable banking whilst making the lives our of customers easier.
(There is also genuine color-change sapphire which mimics alexandrite, as well as color-change garnet that can be a real fooler.). The first thing to do is check the refractive index of the stone, since each material has unique optical properties.
When you mix the Tonal grade and Saturation you will have the color in an emerald. In the market the most expensive emeralds are the ones with high saturation and a Tonal Grade between Medium and Medium Dark. Of course, this doesn't mean that you won't enjoy a Medium Light with nice saturation or vivid green emerald.