Amethyst Buying Guide: Natural vs Heat Treated Amethyst & Citrine
Amethyst Buying Guide: Natural Color vs Heat Treated
Here's the short answer. Most heat treated amethyst isn't sold as amethyst. It's sold as citrine.
That's what trips people up. Heat a piece of purple quartz hot enough and the purple disappears. What's left is yellow, orange or brown quartz, and the trade calls it citrine. Wikipedia's citrine entry says natural citrine is very rare and that most of what's sold under the name is heated amethyst. So an amethyst buying guide has to answer two different questions. How do you know a purple stone is what the seller says it is? And how do you know an orange cluster wasn't purple before it went into an oven?
We'll answer both. After that we'll cover fading, which fools almost everyone and has nothing to do with treatment.
The quick version
- Heat turns amethyst yellow, orange or green. It doesn't make it more purple. A 2020 study in Scientific Reports found the stone stays purple below about 420°C, can turn green between roughly 420 and 440°C, and turns citrine colored above that.
- Heat is also used to lighten very dark stones. GIA lists that as one use, along with clearing brownish tints in some stones.
- Most citrine on the market started as amethyst. Most of it comes from Brazil.
- Heated amethyst is real quartz, not a fake. The problem starts when it's sold as natural citrine without saying so.
- Sunlight fades purple quartz whether it was treated or not. A pale stone on a windowsill tells you where it sat, not what was done to it.
What heat actually does to amethyst
The colors of amethyst, citrine and green prasiolite all trace back to iron in the crystal, which is why heat can move one into another. The change happens in stages. Here's the pattern researchers measured, with Fahrenheit added.
| Heat level | What happens | What you'd see for sale |
|---|---|---|
| Below about 420°C (790°F) | Stays purple. Very dark stones can lighten. | Amethyst |
| About 420 to 440°C (790 to 825°F) | Some amethyst turns green. This stage is unstable. | Prasiolite, often called green amethyst |
| Above about 440°C (825°F) | Turns yellow, orange or brown | Citrine, sometimes called burnt amethyst |
Those numbers come from lab work on test samples. Real treatment varies from stone to stone, and not every stone turns green. Only a few localities produce material that does. The best known is the Montezuma mine in Minas Gerais, Brazil, where heated stones turning green were noticed in the 1950s.
Is that "citrine" really amethyst?
If you're looking at yellow or orange quartz, start here. No single row settles it, so check two or three together.
| What to look at | Points to natural citrine | Points to heated amethyst |
|---|---|---|
| Color | Pale yellow to honey, sometimes smoky | Deep orange, orange red or brown |
| How the color sits | Soft, gradual shifts | Strong contrast, with orange tips running into a chalky white base |
| Form | Single crystals and cut stones | Geode pieces and druzy clusters |
| Price | Costs more than a purple piece of the same size | A large, vivid piece at a very low price |
These tells come from Wikipedia's citrine entry and from dealer guides that cover the same ground.
Heated amethyst isn't a scam. It's the same mineral, and it can look great. A seller who labels it heat treated amethyst is being straight with you. The seller to avoid is the one who calls it natural citrine and charges natural citrine prices.
A pale base doesn't mean your amethyst was heated
It's an easy mix up to make, because a white base is the classic warning sign on orange clusters. On a purple cluster it means something else. Color zoning is normal in natural amethyst. A crystal can be deep purple at the tip and pale lower down with no treatment involved. Wikipedia notes that heated stones show zoning too, so zoning alone proves nothing in either direction.
The base only becomes a flag when the same cluster is bright orange on top.
Can you tell if purple amethyst was heated?
Not reliably by eye. Heating to lighten a very dark stone or clear a brownish tint leaves something that still looks like amethyst. A gem lab can look deeper, but nobody sends a fifty dollar specimen to a lab. In practice you're weighing three things: what the seller tells you, what the piece looks like, and what it costs.
Form helps a little. According to Wikipedia, heated material shows up as druzy and geode pieces, and most of it comes from Brazil. That doesn't prove any one cluster is untreated. It does tell you where to ask more questions. A big, vivid geode half at a bargain price needs more questions than a small crystal cluster still sitting on its host rock, with a locality named and a weight listed. We walked through the same treatment questions for another stone in our natural vs treated tourmaline guide.
Fading has nothing to do with treatment
Ultraviolet light breaks down the color centers in amethyst. The longer a stone sits in direct sun, the paler it gets. Strong heat can drain color too. Heated green prasiolite fades in strong sunlight as well, so treatment doesn't make a stone safer.
So if a stone you bought a few years ago looks lighter, that tells you where it was sitting. Keep specimens on a shelf out of direct sun and away from radiators. Our guide to cleaning and caring for raw mineral specimens covers storage in more detail, and kunzite behaves the same way, as we explain in our Afghan kunzite guide.
What to check before you buy an amethyst cluster
- How it's labeled. It should say amethyst. If it's purple and called something else, or orange and called natural citrine, ask questions.
- Locality. A named country or region tells you more than "natural crystal."
- Size and weight. Listings that give grams or carats let you compare pieces by price per gram.
- Color in more than one photo. Check the tips and the base in daylight. Zoning is normal. Chalky white under orange is not.
- The host rock. A cluster on its matrix, with calcite or siderite alongside, shows how it grew. That context is part of what you pay for.
- The price. A large, vivid orange cluster at a very low price is almost always heated amethyst.
- Treatment disclosure. Ask. A straight answer, or an honest "we don't know," beats silence.
What our amethyst looks like
We list 20 amethyst specimens right now, from $35 to $70. Nearly all come from Afghanistan, and one cluster with calcite comes from Pakistan. They're natural crystal forms, mostly clusters, scepters and twins, and most sit on their host rock. Here are four that show the range.
| Specimen | Locality | Price | What to notice |
|---|---|---|---|
| Scepter Amethyst Quartz Crystal | Afghanistan | $35 | 13.24 g. A scepter has a wider head sitting on a narrower shaft. |
| Etched Amethyst Quartz with Siderite on Matrix | Afghanistan | $55 | 26 g. Natural surface etching, with siderite growing alongside. |
| Amethyst Cluster with Calcite on Matrix | Pakistan | $60 | 52.4 g. Purple quartz and calcite sharing one matrix. |
| Double Terminated Amethyst Crystal on Matrix | Afghanistan | $70 | The highest priced piece in the collection. It has points at both ends. |
Each one is listed as amethyst, in its natural crystal form. Treatment is the one thing a photo can't show you. If you want to know what we know about a specific piece, message us on WhatsApp before you order and we'll tell you.
Browse the full amethyst collection, or look at our wider quartz collection if you want to compare amethyst with other varieties. If you're putting together a first collection, our guide to starting a mineral collection on a budget shows where amethyst in this price range fits.
Frequently asked questions
Is heat treated amethyst fake?
No. Heat treated amethyst is real quartz that has been heated to change its color, usually to yellow or orange. It only becomes a problem when a seller calls it natural citrine without saying it was treated. Reputable sellers label it plainly.
Does heating make amethyst more purple?
No. Heat pushes amethyst toward yellow, orange or green, so it isn't how amethyst gets its purple. GIA's treatment overview describes heating as a way to lighten very dark stones or clear brownish tints in some stones. Darker stones change the most when heated, according to a 2020 Scientific Reports study.
How can I tell natural citrine from heated amethyst?
Look at the color, how it sits in the crystal, the form and the price. Natural citrine is pale yellow to honey with soft shifts. Heated amethyst is usually deep orange, with strong contrast between orange tips and a chalky white base, and it often comes as geode pieces. No single sign is proof, so check two or three together.
Does amethyst fade in sunlight?
Yes. Ultraviolet light breaks down the color centers that make amethyst purple, so stones left in direct sun get paler over time. Strong heat can drain color too. Keep specimens on a shelf away from sunny windows and radiators. Treated or untreated, the same rule applies.
Why is my amethyst cluster white at the bottom?
That's usually natural color zoning. Amethyst often shows zoning, so a crystal can be deep purple at the tip and pale lower down. A white base only raises a flag when the rest of the cluster is bright orange, which is the pattern seen on heated geode pieces.
Not sure about a piece? Send us the listing link and your questions on WhatsApp. We'll tell you what we know before you spend anything.