Prasiolite

Prasiolite is a green variety of quartz. The name prasiolite derives from the Greek πράσον-prason, meaning leeks, and λίθος-lithos, meaning stone. The name literally means leek-colored stone, referring to its color.

Prasiolite

General

Category Tectosilicates, quartz variety

Crystal system Trigonal

Identification

Color Shades of green

Crystal habit Hexagonal prisms

Cleavage None

Fracture Conchoidal

Tenacity Brittle

Mohs scale hardness 7 – lower in impure varieties

Diaphaneity Transparent to nearly opaque

Specific gravity 2.65

Refractive index 1.544 to 1.553

Birefringence 0.009

Ultraviolet fluorescence None

Prasiolite is not a variety of prase, it is an extremely rare mineral in its natural state, because it does not form by normal processes. Normally, prasiolite is a purplish gray amethyst itself rare, (from the Montezuma mine, near Vitoria da Conquista, state of Bahia, Brazil) heated to 650 °C which becomes green and transparent. Usually, amethysts heated in this way turn yellow, and if they are heated more strongly and for a long time, they become colorless. It is because it is only obtained from this variety of amethyst that prasiolite is extremely rare. Naturally, it has been found only very rarely:

Prasiolite is therefore mostly synthetic. Prasiolite is often confused with synthetic green quartz, and only analysis of impurities separates them. Most prasiolite sold is used in jewellery settings, where it can substitute for far more expensive precious gemstones.

Prasiolite is a rare stone in nature; artificial prasiolite is produced from amethyst. Most amethyst will turn yellow or orange when heated, producing heat-treated amethysts which are often marketed as citrine, but some amethyst will turn green when treated. Currently, almost all prasiolite on the market is made from amethyst via a process of heating and irradiation.

Green quartz is sometimes incorrectly called green amethyst, which is not an acceptable name for the material according to Federal Trade Commission Guidelines. Other names for green quartz include vermarine and lime citrine.

The word prasiolite literally means "scallion green-colored stone" and is derived from Greek πράσον prason meaning "leek" and λίθος lithos meaning "stone". The mineral was given its name due to its green-colored appearance.

Natural prasiolite is a very light, translucent green. Darker green quartz is generally the result of artificial treatment.

Remarkable deposits

Since 1950, almost all natural prasiolite has come from a small Brazilian mine, but it has also been mined in the Lower Silesia region of Poland. Naturally occurring prasiolite has also been found in the Thunder Bay area of Canada.

England

North Roskear Mine, North Roskear, Tuckingmill-Illogan Highway area, Camborne - Redruth - St Day District, Cornwall 

United States

Potomac Mine, Leesburg, Loudoun County, Virginia 

France

Le Bourg-d'Oisans, Isère, Rhône-Alpes (Chlorite Quartz) 

Italy

Torre di Rio - Santa Filomena (Monte della Torre), Rio Marina, Island of Elba, Province of Livorno, Tuscany.

Sourced from Wikipedia