Crystal Harvest Field Guide

Amethyst: The Complete Guide

The purple variety of quartz, a former ‘cardinal gem’ once ranked with ruby and sapphire, and the February birthstone. Here’s the real science, history, and geology behind it, from giant Uruguayan geodes to Namibian scepters.

Quick facts

QuartzSiO2, the purple variety of quartz. Trigonal crystal system.
7 on MohsHard and tough enough for everyday jewelry.
SG 2.65RI about 1.54–1.55, birefringence 0.009.
Iron + radiationTrace iron (only ~10–100 ppm) plus natural irradiation creates the purple color centers.
Heat-sensitiveHeated to roughly 300–400 °C it turns yellow to orange, which is how most commercial citrine is made.
Can fadeLong exposure to sun or strong display lights can fade it toward lilac or grey.
FebruaryThe traditional February birthstone.
“Not drunk”The name comes from the Greek amethystos, “not intoxicated.”

The name and the history

For most of history amethyst was a luxury gem. Its fall to an affordable stone is a story about geology, specifically the discovery of enormous deposits in South America.

  1. Ancient EgyptAmethyst is worn and carved as early as about 3100 BC.
  2. Ancient Greece and RomeGreeks believe the stone guards against drunkenness, hence amethystos, “not intoxicated.” Greeks and Egyptians carve drinking vessels from it, and Romans cut it into engraved intaglios.
  3. 1500sThe popular story of Bacchus and a maiden turned into purple stone appears. It is often called an ancient myth, but it was written by the French Renaissance poet Rémy Belleau (1528–1577).
  4. Medieval to 1700sAmethyst ranks among the “cardinal” gems alongside diamond, ruby, sapphire, and emerald. It is set in bishops’ rings and royal regalia. The episcopal ring symbolism refers to the Apostles being “not drunk” at Pentecost.
  5. 1800sLarge deposits in Brazil, and later Uruguay, flood the market, and amethyst becomes an affordable gem.
  6. 1935–1967Amethyst is found near Thunder Bay, Ontario, in 1935. A mine opens there in 1967 and becomes the largest amethyst mine in North America.
  7. 1960s–1970sBolivia’s Anahí mine, the world’s only commercial source of natural ametrine, is rediscovered and reaches the market.
  8. 2007The “Empress of Uruguay,” a 3.27 m amethyst geode weighing about 2.5 tonnes, is found near Artigas.
  9. 2022The Los Catalanes district of Artigas, Uruguay, famous for giant geodes, is named an IUGS Geological Heritage Site.

How amethyst forms

Amethyst forms in two main settings: gas pockets in ancient lava flows, and hydrothermal veins cutting through older rock. Either way, it needs iron, silica, and natural radiation.

  1. Lava cools. In South America, huge Cretaceous flood basalts (the Paraná province) cool with trapped gas bubbles that leave hollow cavities called protogeodes.
  2. Water moves in. Later, groundwater seeps through the basalt and into the cavities, carrying dissolved silica.
  3. Layers build up. In the Uruguayan geodes minerals deposit in order: a green clay mineral (celadonite), then agate, then colorless quartz, then amethyst.
  4. Iron gets in. Small amounts of iron replace silicon in the growing quartz structure.
  5. Radiation colors it. Over time, natural radiation from the surrounding rock alters the iron sites into color centers that absorb light and turn the crystal purple.
  6. Or in veins. Elsewhere, such as Four Peaks, Arizona, and Thunder Bay, Ontario, hot iron-bearing water deposits amethyst in fractures and faults instead of lava cavities.

Formation temperature in the giant geodes is still debated: fluid-inclusion studies suggest about 50–120 °C, while oxygen isotopes point to as low as about 24 °C.

Where amethyst is found

Amethyst is found on every inhabited continent, but a handful of localities define the market and the collector world.

Brazil

Rio Grande do Sul & Pará

The world’s largest producer. Basalt cavities can hold hundreds of kilograms to tonnes of crystals. Production was reported at 10,977 tonnes in 2014.

Uruguay

Artigas

Famous for deep-purple geodes and cathedral-sized mega-geodes from the Arapey Formation basalts.

Zambia

Kalomo area

Around 1,000 tonnes a year of saturated, often raspberry-toned amethyst, typically more included than Brazilian material.

Namibia

Brandberg & Goboboseb

Crystals from roughly 132–135-million-year-old Etendeka basalts, known for scepters, smoky zones, and inclusions.

Canada

Thunder Bay, Ontario

Fault-controlled veins in ancient Archean rock, often with red hematite tips. North America’s largest amethyst mine.

USA

Four Peaks, Arizona

The only active commercial amethyst mine in the US, at about 6,600 ft and reachable only on foot or by helicopter. Known for red flashes.

Mexico

Veracruz

Slender, elongated crystals, usually 1–2 inches, pale lilac to royal purple, found in andesite. Supply has largely stopped.

Russia

Ural Mountains (Mursinka)

Historic source of the finest deep-colored material. The old mines are described as depleted.

Record breakers

  • Empress of Uruguay: 3.27 m tall and about 2.5 tonnes, found in 2007 near Artigas and displayed at the Crystal Caves in Atherton, Australia. Often called the world’s largest amethyst geode.
  • A roughly 5 m, 14-tonne Uruguayan geode offered at auction in 2020 challenges that title, so “largest” depends on the source.
  • Single amethyst crystals over 30 cm long are very rare.

Varieties and trade names

“Siberian” and “Deep Russian”

Color grades, not origins. “Siberian” means about 75–80% purple with red and blue flashes, from anywhere in the world.

Rose de France

Pale lilac to lavender. Once undesirable, now popular.

Ametrine

Purple and yellow zones in one crystal, caused by different states of iron. Natural ametrine comes commercially from Bolivia’s Anahí mine.

Prasiolite

Green quartz, nearly always heat-treated amethyst from specific deposits. Under FTC guidance, “green amethyst” is not an acceptable name.

Chevron

V-shaped bands of purple and white quartz from vein deposits.

Scepters

A later amethyst crystal grown over the tip of an earlier crystal, a Brandberg specialty.

Hematite-included

Red to rust flecks of hematite, as in Thunder Bay’s red-tipped crystals.

Botryoidal amethyst

Grape-like clusters of tiny crystals, often misnamed “grape agate.”

Treated, synthetic, and look-alike amethyst

Amethyst is one of the most treated and synthesized gems in the trade. Here’s what to know.

PropertyWhat it isClues
Heated amethyst (“citrine”)Amethyst heated until it turns yellow, orange, or brown. Most commercial citrine is made this way.Deep orange, “burnt” tones, and orange tips on white-based geode clusters. Heated stones lack the dichroism of natural citrine.
PrasioliteGreen quartz from heated or irradiated amethystSold as “green amethyst,” a name the FTC rejects
Synthetic amethystGrown hydrothermally in high-pressure autoclaves since before 1970, notably in Russia. Russia has produced synthetic ametrine since 1994.Natural stones usually show Brazil-law twinning under a polariscope, plus angular color zoning and “tiger stripe” fingerprint inclusions. Some stones need infrared spectroscopy, so a lab is the only sure answer.
Dyed or filledPale quartz dyed purple, or fractures filledColor concentrated in cracks. Avoid ultrasonic cleaning.

Myths vs. facts

Myth: All amethyst comes from Brazil.

Fact: Brazil is the biggest producer, but Uruguay, Zambia, Bolivia, Canada, Russia, Mexico, Namibia, and the US all produce it.

Myth: The Bacchus legend is an ancient Greek myth.

Fact: It was written by the French poet Rémy Belleau in the 1500s. The ancient part is only the name’s link to being “not intoxicated.”

Myth: Amethyst prevents drunkenness.

Fact: That was an ancient belief, and it’s where the name comes from. It has no scientific basis.

Myth: “Siberian amethyst” comes from Siberia.

Fact: It is a color grade and can come from anywhere.

Myth: Green amethyst is a natural gem.

Fact: Green quartz sold under that name is usually heat-treated amethyst, correctly called prasiolite.

Myth: Amethyst was always cheap.

Fact: It was a cardinal gem on par with ruby and sapphire until huge South American deposits were found.

Myth: Amethyst’s color is permanent.

Fact: Strong light and heat can fade or change it.

Care and display

Keep it out of the sun

Prolonged sunlight or strong display lighting can fade the purple. A shaded shelf or cabinet is best.

Avoid heat

Heat, steam cleaners, and sudden temperature changes can crack it or change its color.

Cleaning

Warm soapy water and a soft brush. Ultrasonic cleaning is usually fine unless the stone is dyed or fracture-filled.

Chemicals

Keep away from hydrofluoric acid and strong alkaline cleaners.

Amethyst in the shop

Hematite Included Amethyst Cluster Set — 4 Natural Specimens
Hematite Included Amethyst Cluster Set — 4 Natural Specimens$32.00
Eight pale yellow tumbled citrine stones on a white background beside a steel caliper for scale
Pale Citrine Tumbled Stones Lot$13.12
Hand holding a lavender amethyst cluster from Brazil, pale purple points over dark grey-green volcanic matrix
Lavender Amethyst Cluster — Brazil$19.00
Hand holding a small Brandberg amethyst cluster from Namibia, smoky grey-purple points on a dark base
Amethyst Cluster — Brandberg, Namibia (Small Specimen)$14.76
Hand holding a single Brandberg amethyst crystal from Namibia, pale purple point on a yellow-green matrix base
Amethyst Crystal — Brandberg, Namibia$45.92
Parcel of twenty natural Brandberg amethyst points from Namibia scattered on white beside a caliper
Brandberg Amethyst Point Parcel — Namibia, 20 Natural Points$101.68
Hand holding a Brandberg amethyst cluster from Tafelkop, Namibia, pale purple points with iron staining
Brandberg Amethyst Crystal Cluster — Tafelkop, Namibia$45.92
Six natural Brandberg amethyst crystals from Namibia laid out on white beside a caliper
Brandberg Amethyst Crystal Lot — Namibia, 6 Natural Points$55.76
Amethyst crystal cluster plate with deep purple points, shown on white beside a caliper for scale
Amethyst Crystal Cluster – Natural Purple Quartz Specimen$49.20
Hand holding a large vintage amethyst crystal cluster with well formed purple points
Amethyst Crystal Cluster – Vintage Collection Specimen$45.92
See all amethyst

Frequently asked questions

Why is amethyst purple?

Trace amounts of iron in the quartz structure, altered by natural radiation, create color centers that absorb light and make the crystal look purple.

Does amethyst fade?

It can. Long exposure to sunlight or bright display lights can fade it toward lilac or grey, so keep prized pieces out of direct sun.

Is amethyst hard enough for rings?

Yes. At 7 on the Mohs scale with good toughness it wears well, though it can still chip with hard knocks.

What is the largest amethyst geode?

The Empress of Uruguay (3.27 m, about 2.5 tonnes) is widely cited, but a roughly 5 m, 14-tonne Uruguayan geode auctioned in 2020 may be larger.

Can I tell synthetic amethyst from natural by eye?

Usually not reliably. Gemologists use polariscope twinning patterns, color zoning, inclusions, and sometimes infrared spectroscopy.

What month is amethyst the birthstone for?

February.

Is citrine just heated amethyst?

Most commercial citrine is. Natural citrine exists but is rarer and usually paler.

Can amethyst go in water?

Yes. Amethyst is quartz, which is hard and does not dissolve in water, so rinsing it is safe. Avoid hot water and sudden temperature changes, which can crack included or fractured stones, and be careful with clusters on matrix or pieces with glued bases, which can loosen when soaked. Dry it indoors, not in the sun.

Can I wear amethyst in the shower?

The stone itself will not be harmed, but soap and shampoo leave a dull film, and the metal setting may tarnish or loosen over time. It is best to take amethyst jewelry off before showering or swimming.

What should you not do with amethyst?

Do not leave it in direct sunlight for long periods (it can fade), do not heat it (heat turns it yellow or orange, which is how most “citrine” is made), avoid harsh chemicals, and do not put fractured stones in an ultrasonic cleaner. Store it away from harder gems that can scratch it.

How can you tell if amethyst is high quality?

Look for rich, even purple color with no obvious paler zones, ideally with flashes of red or blue in good light, and good transparency without visible cracks or cloudiness. Deeply colored, evenly saturated material is often traded as “Deep Siberian.” For specimens, sharp, glossy points and an undamaged cluster matter more than clarity.

What is the rarest amethyst color?

The most prized is a deep, saturated purple with red and blue flashes. Very pale lilac material is common and less valuable. Naturally green quartz (prasiolite) is rare in nature; almost all green “amethyst” on the market has been heated.

What does the Bible say about amethyst?

Amethyst appears twice: as one of the twelve stones on the high priest’s breastplate in Exodus 28, and as the twelfth foundation stone of the New Jerusalem in Revelation 21:20. Read more in The 12 Stones of the Bible.

What does the name amethyst mean?

It comes from the ancient Greek amethystos, meaning “not intoxicated,” from an old belief that the stone protected its wearer from drunkenness.

Is amethyst a type of quartz?

Yes. Amethyst is purple quartz, silicon dioxide (SiO2), colored by trace iron and natural radiation. Shop our amethyst specimens.

Keep reading

Sources and further reading

Where sources disagree, such as heating temperatures and the “largest geode,” this page gives both figures.

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