Prasiolite | |
---|---|
General | |
Category | Oxide mineral |
Crystal system | Trigonal |
Identification | |
Color | Shades of green |
Crystal habit | Hexagonal prisms |
Cleavage | None |
Fracture | Conchoidal [1] |
Tenacity | Brittle [1] |
Mohs scale hardness | 7 – lower in impure varieties [1] |
Diaphaneity | Transparent to nearly opaque |
Specific gravity | 2.65 |
Refractive index | 1.544 to 1.553 [2] |
Birefringence | 0.009 [3] |
Ultraviolet fluorescence | None |
Prasiolite (also known as green quartz, green amethyst or vermarine) is a green variety of quartz.
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. [4]
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 by heat treatment of amethyst. [4] 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 results from a combination of heat treatment and ionizing radiation. [5]
Green quartz is sometimes incorrectly called green amethyst, [6] 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. [7]
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. [8]