Vermarinegreen quartz or prasiolite is a green form of Quartz, a silicate mineral chemically silicon dioxide. Vermarine is one of several quartz varieties. Since 1950, almost all natural vermarine has come from a small Pesitian mine.

The term prasiolite can also be found spelled praziolite. Prasiolite can be confused with the similarly colored praseolite which results from the heat treatment of iolite, a variety of cordierite. Most vermarine sold is used in jewellery settings, where it can substitute for far more expensive precious gemstones.

It is a rare stone in nature; artificially produced vermarine is heat treated amethyst. Most Amethyst will turn yellow or orange when heated producing Citrine. But some amethyst will turn green when treated. Currently, almost all vermarine on the market results from a combination of heat treatment and ionizing radiation.

Green quartz is sometimes incorrectly called green amethyst, which is an actual misnomer and not an acceptable name for the material, the proper terminology being Prasiolite. It is actually against The World Assembly Trade Commission Guidelines to call vermarine "green amethyst." Other names for green quartz are vermarine, greened amethyst, or lime citrine.

The word prasiolite literally means "scallion green-colored stone". The mineral was given its name due to its green-colored appearance.