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Amethyst under a microscope!
image location - microscopy.fsu.edu |
Postage stamps dedicated to Amethyst!
image location - stampmin.home.att.net |
Amethyst is the purple variety of quartz, and is closely related to other varieties of
quartz such as citrine, smoky quartz, rose quartz, and even aventurine, agate, carnelian and
opal. The purple color of amethyst is due to iron impurities at specific sites in the
crystalline structure. If the iron impurities within the crystal are highly oxidized, the gem
takes on the deep purple of an amethyst. If the mineral is heated, the oxygen is removed from
the iron and the gem fades and will turn brown then yellow, green or colorless depending on
the location of the iron within the crystal. If it turns yellow, it is then known as a citrine.
The purple color can be restored through irradiation, which re-oxidizes the iron. The process
can be natural, or produced in a laboratory, and can be repeated several times unless the
distribution of the iron impurities is changed, usually through excessive heating. It is not
possible to determine if the gem started life as an amethyst or citrine, or if it was
naturally or synthetically changed.
Most amethyst stones used in jewelry come from either Africa or South America. Uruguay
produces some of the finest amethyst specimens, but high quality stones are also found in
Brazil, Bolivia, Argentina and Mexico. Zambia, Namibia and other African countries are also
major producers of amethyst. Canada, Russia, Germany, Austrilia Italy and the United States
all produce small quantities of amethyst.
| Composition | SiO2 with minor Fe4+ | Class | Tectosilicate |
| Specific gravity | 2.65 | Refractive Index | 1.54 to 1.55 |
| Birefringence | weak (.009) | Pleochroism | distinct |
| Cleavage | none | Fracture | conchoidal |
| Luster | vitreous | Transparency | transparent to translucent |
| Streak | white | Fluorescence | Weak blueish |
| Crystal system | Hexagonal | Twinning | Dauphine and Brazil twinning |
| Hardness | 7 | Dispersion | .013 |
| Color
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The color of Amethyst will vary greatly depending on where it comes from. The color tone is dependant on the amount of iron impurities in the stone, and the degree of radiation damage done. Gems that come from South America tend to be larger and lighter than those from Africa, but this is only a very general statement. Mexican amethyst specimens from Vera Cruz are usually very pale, while those from Guerrero are generally very dark. Brazilian amethyst is usually in the form of a drusy with a light to medium color, often with heavy inclusions. Uruguay produces fine amethyst specimens that have a very uniform medium to dark color. African stones can be quite large and not very attractive until the stone is cut to reveal a darker and clearer center. Amethyst from Thunder bay in Canada often is of a more reddish tint while those from Pennsylvania tend to have a brownish tint, and those from North Carolina have a bluish tint.Amethyst from the Ural mountains in Russia are very clear and very dark, but those from Germany are light |
| Crystal habit | Amethyst crystals form in macroscopic, horizontally striated hexagonal prisms terminated by a combination of positive and negative rhombohedrons forming six sided pyramids. It often occurs as drusy masses showing only the rhobohedral terminations but can also be massive. |
| Other | Because Amethyst is quartz, the most common material on earth, it is part of the dust in the air that can scratch softer materials. Therefore, quartz (hardness of 7 on the Mohs hardness scale) is considered the benchmark of a gem's hardness. Gems that have a hardness of under 7 are considered "soft" and require special care since they can be scratched by dust, which has a hardness of 7. |
The name "Amethyst" comes from the Greek "Amethustos", which means "not drunken". It was
so named because of its color and the belief that a person drinking wine from a cup carved
from amethyst could not become intoxicated. It may be that those who did not get drunk were
actually drinking water, but because of the color of the cup, no one could tell.
The legend of the origin of amethyst comes from Greek myths. Dionysius, the god of
drunkenness, was angered one day by an insult from a mortal and swore revenge on the next
mortal being that crossed his path. He created fierce tigers to carry out his wish. Along
came unsuspecting Amethyst, a beautiful maiden on her way to pay tribute to the goddess Diana.
To protect her from the wrath of Dionysius, Diana turned Amethyst into a stature of pure
crystalline quartz to protect her from the brutal claws of the tigers. At the sight of the
beautiful statue, Dionysius wept tears of wine in remorse for his evil deed. The god's tears
stained the quartz purple, creating the gem we know today as amethyst.
