Some amethysts from certain localities change colour to green when heated under appropriate condition. They are known as “prasiolite” or green amethyst. A large amount of green quartz in a similar colour has been on the gem market recently and are for sale quite cheaply. When studied it was proved that they were not greened amethyst but actually irradiation-treated quartz. Synthetic green quartz, although in small quantity, is also available on the market. Identification of green quartz is becoming more complicated today because of these factors.
 

Location -USA, Africa, Russia and various places in the world.

Group - Quartz

R.I. - 1..544-1.553

Hardness - 7