It's Prasiolite, a form of green quartz (silicon dioxide SiO2) also know as vermarine but not green amethyst or greened amethyst considered misnomers by gemologists. It is usually produced artificially by heat-treating amethyst to over 900 degrees F. but natural deposits have been found. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, Arizona and some from Poland. Recently quartz has appeared on the market that has been turned green by irradiation.
It has a Refractive Index of 1.55 and Specific Gravity of 2.65 with harness of 7 on the Moh's Scale, making it a durable stone for jewellery.
Intensity of colour and fine clarity are the most important aspects when buying a cut gem. The colour variations go from a pale yellow-green to a deeper, more lustrous green.
And this is going on my wish list along with the three or four hundred other gems I'd like.
The Mystic Lore:
Intuitive sources say that Prasiolite helps to link the physical and spiritual aspects of life, activating the heart as one's centre of conscious. It is said to strengthen one's mind, emotions and will, and to attract prosperity.