PRASIOLITE the green variety of quartz

PRASIOLITE, the green variety of quartz

VARIETY INFORMATION:

VARIETY OF: Quartz , SiO 2 .
USES: Gemstone and ornamental stone.
COLOR: a pale lime-green
INDEX OF REFRACTION: 1.544-1.553
BIREFRINGENCE: 0.009
HARDNESS: 7
CLEAVAGE: none
CRYSTAL SYSTEM: trigonal
For natural prasiolite mineral specimens see our For Sale or Sold lists

Prasiolite (or vermarine) is the name for any quartz crystal or cluster that is green in color. Although often cut as a gemstone, prasiolite is actually quite rare in nature. Most prasiolites on the market are heat treated amethyst. When heat treated, the amethyst from most locations transforms into yellow or orange citrine. From a few locations, a green color results, yielding prasiolite which is often called (wrongly) "green amethyst". These locations include Montezuma, Brazil, and Arizona. Naturally occurring prasiolite has been reported from Poland.

Prasiolite (sometimes spelled praziolite) can be confused with the similarly colored praseolite which results from the heat treatment of iolite, a variety of cordierite. Note the spellings: prasiolite is the quartz variety, while praseolite is the cordierite variety - not the other way around (which would be easier to remember).

Note that prasiolite is macro-crystalline quartz. A green cryptocrystalline quartz, where the individual crystals are too small to be seen and the resulting transparency is translucent, would be called chrysoprase. The term prase is sometimes used for any leek-green color of quartz, whether macro- or cryptocrystalline.

Some colorless quartz crystals have sufficient inclusions of chlorite to result in a green color. However, this would not be considered prasiolite. In any event, the color is wrong - more of a dark grass-green than a leek-green.

Prasiolite is only one of several quartz varieties. Other varieties that form macroscopic (large enough to see) crystals are as follows:

Amethyst is the purple gemstone variety.
Citrine is the yellow to orange gemstone variety.
Milky Quartz is the cloudy white variety.
Rock crystal is the clear variety that is also used as a gemstone.
Rose quartz is a pink to reddish pink variety.
Smoky quartz is the brown to gray variety.