Amethyst is crystalline quartz in colors ranging from pale lilac to deep reddish purple. With a relatively high hardness of 7 and no special care requirements, the February birthstone is a fine facetable jewelry gem for all purposes. Lower grades of material can be cabbed, carved, and made into a great variety of beads and other ornamental objects.
Value for amethysts depends almost entirely on color. Siberian mines once produced the world's finest stones. They featured a particularly rich purple color that glowed with red and blue flashes. Today the term “Siberian” no longer refers to origins. Instead, this is now a trade and grade term referring to colors similar to those of the amethysts mined in Siberia. Stones with Siberian color command the highest prices.
Since amethyst is readily available in large sizes, its value per carat climbs gradually, not exponentially. Since this stone is plentiful, there is little reason to pay top dollar for pieces with visible inclusions or inferior cutting.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Is a Variety of||Quartz|
|Refractive Index||1.544 – 1.553|
|Colors||Pale lilac to deep reddish purple|
|Fracture||Conchoidal to uneven|
|Cleavage||None or indistinct|
|Luminescence||Inert to weak blue in SW. Inert in LW.|
|Wearability||* Very Good|
|Enhancements||Amethyst can be heat treated to improve the color or change it to citrine. Not common.|
|Transparency||Transparent to translucent|
|Absorption Spectrum||550-520 nm|
|Pleochroism||Weak to moderate, purple and reddish purple.|
|Optics||o = 1.544; e = 1.553 (very constant). Uniaxial (+)|
|Etymology||From the Ancient Greek amethystos, meaning “not drunk.” It was believed you could drink all night and remain sober if you had an amethyst in your mouth.|
|Occurrence||Generally in pegmatites and veins. Found in geodes in alluvial deposits.|
|Inclusions||Prismatic crystals and negative cavities, thumbprint marks, so-called rippled fractures, and twinning lines.|
Although Siberian reigns atop the value listing, light colored amethyst has enjoyed a resurgence in popularity. The lightest, pinkish violet shades are called “Rose de France,” a clever bit of marketing. The artistry of gemstone faceting can shine through these gems if given fancy and unusual cuts.
This variety of quartz receives its color from the presence of iron and other trace elements as well as natural irradiation.
Amethyst has popular associations with purity, spirituality, and the calming of passions. Perhaps the most famous bit of folklore for this stone connects it to the prevention of drunkenness. For more on myths and traditional beliefs relating to this gemstone, see our symbolism article.
- Heat treatments can lighten amethyst, turning it green, blue, or yellow/orange. (Occasional, undetectable, stability excellent).
- When heated to 400–500º C, amethysts may turn brown, red, and sometimes a green color. These green gems are sometimes sold as “greened amethyst” or prasiolite.
- Heat treatments of both natural and synthetic amethyst can produce similarly colored material (ametrine). Such stones are indistinguishable from natural ones.
- Irradiation plus heating may also produce brown, orange, and yellow hues.
Today’s major sources are Brazil, Bolivia, Uruguay, and Zambia. Brazilian stones can be found in huge sizes but are generally moderate in color. They often show color-banding, despite the best efforts of cutters to minimize it. Many gem enthusiasts prefer the usually smaller but more richly colored stones from Zambia and, more recently, from Uruguay.
Brazil; Bolivia; Zambia; Russia; Namibia; Australia; Nigeria; India; Uruguay; Mexico: Arizona; North Carolina.
In terms of size, amethyst is one of the exceptions of the quartz family. Most quartz can grow quite large and be cut into gems weighing thousands of carats. However, there are few clean examples of amethysts of 100 or more carats.
Amethyst is rare in very large, transparent masses. The fine gems at the Smithsonian Institution (Washington, D.C.) are exceptional, such as the 1,362-carat Brazilian stone and the 202.5-carat stone from North Carolina.
- Siberian amethyst: dark purple color with flashes of red and/or blue.
- Golden amethyst: ametrine.
Amethysts that are heated to a brownish yellow color are sometimes sold as “Madeira topaz.” Stones with lighter shades are sometimes sold as “Palmyra topaz.” Amethysts that are heated to a reddish color are sometimes sold as “Spanish topaz.”
Violet sapphire is sometimes referred to erroneously as “Oriental amethyst.”
Kunzite is sometimes referred to erroneously as “Lithia amethyst.”
These names are misleading and should not be used. Amethyst is a distinct gem species from topaz, sapphire, and kunzite. Consult our List of Gemstones with False or Misleading Names for more examples.
See our Gemstone Care Guide for recommended cleaning methods.
by Dr. Joel Arem; Donald Clark, CSM IMG; Barbara Smigel, PhD GG