Prasiolite

Prasiolite, green-quartz or vermarine is a green form of quartz, a silicate mineral chemically silicon dioxide. Prasiolite is one of several quartz varieties. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, but it is also seen in Lower Silesia in Poland. Naturally-occurring prasiolite is also found in the Thunder Bay area of Canada.

Prasiolite and also be found spelled praziolite. Prasiolite can be confused with the similarly coloured praseolite which results from the heat treatment of iolite, a variety of cordierite.

It is a rare stone in nature. Most prasiolite sold is jewellery settings. Prasiolite is heat treated amethyst. Most amethyst will turn yellow or orange when heated producing citrine. But some amethyst will turn green when treated.

The name is derived from Greek prason meaning "leek" and lithos meaning "stone". This means that "prasiolite" literally means "garlic green-coloured stone". The mineral was given its name due to its green-coloured appearance.

Source

 * http://en.wikipedia.org