How to Recognise a Real Amethyst: Natural, Synthetic, Dyed or Glass
Natural amethyst, lab-grown, dyed quartz or violet glass: colour clues, the trap of geodes, misleading names and simple, safe tests.
Key points
| Nature | violet quartz (SiO2), colour due to iron and natural irradiation |
|---|---|
| Hardness (Mohs) | 7 |
| Density | about 2.65 |
| Cases to tell apart | natural, synthetic (hydrothermal), dyed quartz, glass, heated quartz |
| Deposits | Brazil, Uruguay, Zambia, Madagascar, Bolivia, Russia, France (Auvergne) and others |
| Heated | turns yellow to orange (citrine) or sometimes green (prasiolite) |
| Sensitivity | may fade with prolonged bright light |
| If the piece is valuable | certificate from a gemmological laboratory |
A common stone with many variants
Amethyst is the violet variety of quartz. Its colour comes from traces of iron and from natural irradiation undergone underground. It is widespread (Brazil, Uruguay, Zambia, Madagascar, Bolivia and many other places), which explains its affordable prices. Its appearance ranges from pale lilac to deep purple.
On the market, several forms coexist:
- Natural amethyst, rough in clusters, geodes and points, or cut.
- Heated amethyst: transformed into yellow or orange (sold as citrine) or sometimes green (prasiolite). Partial heating gives ametrine.
- Synthetic amethyst: grown in a laboratory in an autoclave. It has the same composition and properties as natural amethyst.
- Dyed quartz: colourless, often fissured quartz, coloured violet. Agate and chalcedony dyed violet also exist.
- Violet glass: points, balls and moulded beads.
Warning signs
| Sign | Natural amethyst | Dyed quartz, glass or other |
|---|---|---|
| Colour | Uneven zones, angular bands, more intense at the points and on certain faces | Perfectly uniform violet; colour concentrated in the fissures (dye) |
| Fracture | Shell-shaped, shiny chips | Glass: round bubbles, moulding striae |
| Crystals in a cluster | Points of varied sizes, with horizontal striations on the faces | Identical points, as if from the same mould |
| Inclusions | Veils, irregular fissures, solid inclusions | No natural inclusions or bubbles |
| Temperature | Stays cool for a long time | Glass: warms up faster; plastic: lukewarm |
| Price | Depends on size and colour | Very low for a large ball or a large cut stone of deep violet |
Beware of dyed geodes and clusters, especially those in vivid colours (electric violet, blue, pink): agate and quartz druses are frequently coloured.
Simple and safe tests
- Read the description: “natural”, “synthetic”, “heated”, “dyed”. Ask for details if nothing is stated.
- Look under a magnifier: round bubbles indicate glass, colour in the fissures indicates dye, irregular inclusions are natural.
- Look for colour zoning: light passing through the stone often reveals patches or bands of different shades, oriented according to the faces. A completely uniform violet is rarer.
- Rub a slightly damp white cotton pad (lukewarm water) over an inconspicuous spot: a coloured pad reveals dye.
- Compare several points of a cluster: shape and tint vary in natural specimens.
- Feel the temperature: quartz feels cooler than glass on first contact, which is only an indication.
No acid, no flame and no blade. A scratch test would mark the piece and brings nothing useful here.
What these tests cannot prove
Synthetic amethyst cannot be recognised by eye: it has the same composition as natural amethyst. Laboratories look for a special twinning known as the “Brazil law”, visible under a polariscope, along with other clues, but this requires instruments. Price differences are modest for common stones, but significant for fine cut stones.
A deep, very pure violet is no proof either way. For a valuable piece, a certificate from a gemmological laboratory is the only guarantee. For decoration, reading the description and trusting the seller matter more.
Useful questions to ask the seller
A few questions are often enough to clear up doubts. Is the stone natural or synthetic? Has it been heated or dyed? Is it a cluster cut from a single block, or pieces glued together? Have the points been glued onto a support? Where does the stone come from?
Amethyst clusters and geodes from Brazil and Uruguay are sometimes made of points glued onto a resin or plaster base: a base that is too regular, a line of glue, or points all oriented the same way should draw your attention. A very low price for a large, deep cluster is possible (amethyst is abundant), but it is worth understanding what explains that price.
Misleading names, colour and care
- “Green amethyst” refers to prasiolite: green quartz, which occurs naturally in rare deposits or is obtained by heating amethyst. The name is misleading.
- “Oriental amethyst” refers to a violet sapphire or spinel: a different mineral.
- “Amethyst root” refers to violet fluorite.
Amethyst can lose some of its colour under prolonged bright light or heat: avoid leaving it in full sun for months. For care, see amethyst. In our shop, the nature of each piece is stated on its sheet: our commitments.
Frequently asked questions
How can you recognise a real amethyst?
Look for irregular colour zoning, natural inclusions and points of varied shapes. Round bubbles, colour in the fissures or a perfectly uniform violet suggest glass or dye. Only a laboratory can settle the question if in doubt.
Is synthetic amethyst a fake amethyst?
It has the same composition as natural amethyst, but it is made in a laboratory. It must be sold as synthetic. Only a laboratory can tell it apart from natural amethyst.
Are very vivid violet geodes natural?
Very vivid shades (electric violet, blue, pink) are often produced by dyeing quartz or agate. Genuine amethyst geodes have more nuanced tones.
Does amethyst fade in the sun?
Yes, it can lose colour if it stays in strong light for a long time. Keep it out of full sun.
What is heated amethyst?
It is amethyst that has been heated, turning yellow to orange (sold as citrine) or sometimes green (prasiolite). It is a common and long-established treatment.
Also read
The meanings mentioned belong to tradition and symbolism. They are neither promises of results nor medical advice. Back to Recognizing real stones.