Amethyst
Silicon dioxide (SiO₂)
The purple variety of quartz, colored by iron and natural irradiation, prized as the classic violet birthstone of February.
- Mohs hardness
- 7
- Color
- Pale lilac to deep violet-purple
- Type
- crystal
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Overview
Amethyst is the violet to purple variety of crystalline quartz, one of the most popular and recognizable gemstones in the world. Its color ranges from a faint lilac to a rich, saturated grape-purple, and the most valued stones show a deep, even violet with subtle red flashes.
The purple color comes from trace amounts of iron combined with natural gamma irradiation deep in the Earth, which creates color centers within the silica lattice. Historically, amethyst was considered a precious stone on par with emerald and ruby until large Brazilian deposits made it abundant and affordable.
It is the birthstone for February and has been carved, faceted, and worn since antiquity for both ornament and supposed protective powers.
Formation & geology
Amethyst forms primarily in gas cavities (vugs) within volcanic rocks such as basalt, where silica-rich fluids slowly precipitate quartz crystals onto cavity walls. These hollow, crystal-lined nodules are called geodes.
The characteristic purple color develops when trace iron (Fe) is incorporated into the growing quartz and is then exposed to natural radiation from surrounding rocks over geological time, producing color centers.
Major deposits occur in Brazil (Rio Grande do Sul), Uruguay, Zambia, and Madagascar, with notable historic sources in Russia (the Ural Mountains) and the United States. Heating amethyst can turn it yellow-orange, producing most commercial citrine.
How to identify it
- Color: Purple to violet, often zoned (color concentrated near crystal tips). Color banding under magnification is a strong clue.
- Hardness: 7 on the Mohs scale; it will scratch glass and steel easily and resist scratching by a knife.
- Luster: Vitreous (glassy); transparent to translucent.
- Crystal form: Six-sided prisms ending in pyramid points, often as druzy crusts inside geodes.
Look-alikes: Purple glass and synthetic amethyst can mimic it; glass often has rounded edges, bubbles, and lacks color zoning. Purple fluorite is much softer (4) and shows octahedral cleavage. Genuine amethyst feels cool and is hard to scratch.
Uses & significance
Amethyst is mainly a gemstone, faceted for rings, pendants, and earrings, and carved into beads, cabochons, and decorative geodes. Cathedral geodes are popular display pieces.
Because it is abundant, it is affordable despite its beauty; value rises sharply with deep, even color and good clarity (top grades are sometimes called "Siberian").
In metaphysical traditions, amethyst is associated with calm, sobriety, and clarity of mind—its Greek name means "not intoxicated." These uses are cultural and not scientifically established.
Frequently asked questions
Is amethyst rare or valuable?
Amethyst is not rare—large Brazilian and African deposits make most grades affordable. Value depends on color saturation, with deep, even violet stones commanding the highest prices.
How can you tell real amethyst from glass?
Real amethyst is hardness 7 and scratches glass, often shows color zoning, and feels cool. Glass imitations may have air bubbles, rounded molded edges, and uniform color.
Why does some amethyst fade?
Prolonged exposure to strong sunlight or heat can fade amethyst's purple color because the color centers are unstable; store it away from direct sun.
Is amethyst the same as citrine?
Both are quartz. Heating amethyst alters its iron color centers to yellow-orange, producing most commercial citrine; the two can occur together as ametrine.
Amethyst guides
In-depth guides for identifying, valuing, and understanding Amethyst.
Amethyst identified by the community
Real specimens identified with Rock Identifier.
