Prasiolite is often called Green Amethyst which is really a misnomer, much like calling Citrine 'Orange Amethyst'.
Normally when Amethyst is heated it turns into Citrine. But not always.
Amethyst from the Montezuma Mine in Brazil when heated carefully turns green instead and the real name of this material is Prasiolite.
Just like Citrine, though much more rarely, Prasiolite can be found naturally but it's safer to say that all the Prasiolite you see is heated treated Amethyst.
I do test the Thermal Conductivity of all our Prasiolite to prove that it is heated Amethyst, not a hydro quartz, but there's no test to prove whether it's 100% natural or heated material.
