Maya green is made exclusively from natural indigo.
The Maya part of the name comes from the Mayans who discovered that depending on how long the indigo was heated during production different hues could be produced from the classic deep purples, to greens and even yellows. They also found if the indigo was bound to clay particles it became much more stable as a paint.
In masstone this paint is an extremely dark green, with the green hue barely distinguishable due to the very dark tonal value. It is pretty opaque and little is revealed by spreading it thinly.
However once white is added it shows itself as a cool green, not a million miles from Viridian however not quite as acidic and cold. Like all these natural pigments, there is subtlety and a gentleness so frequently lost in modern pigments.
A wide range of tints are produced and if you want a non-toxic, natural Viridian type hue this is for you!