Real amethyst is purple quartz, and the quickest way to tell it from glass is to look inside it with a loupe. Natural amethyst shows uneven color: angular patches, bands or wedges of deeper and paler purple that follow the crystal's growth, often with a faint reddish flash from one angle and a bluish one from another. Glass shows round gas bubbles, swirled streaks and a perfectly even color from every angle. Amethyst also feels cool against the lip and stays cool for a moment, scratches a glass bottle without being scratched by it, and never shows the soft rounded edges that glass facets get after a few years of wear. A stone that has zoning, no bubbles and sharp facet edges is quartz, and purple quartz is amethyst. The harder question is whether it grew in the ground or in a laboratory autoclave, because synthetic amethyst has been made since the 1970s, costs a dollar or two a carat, and looks the same to the eye. That one is a gem lab question. For most jewelry it does not change the price much, because even natural amethyst is one of the least expensive gems there is.
Quick answer
- Natural amethyst: angular color zoning, weak two-color flash when tilted, cool to the touch, scratches glass, no round bubbles.
- Glass: round bubbles, swirls, even color, warmer feel, facets scratch and chip over time.
- Synthetic amethyst: passes every home test; only a lab separates it, and the price difference is small.
- Values as of late 2026: about $2-10 per carat for commercial amethyst, $20-60 per carat for deep Siberian-color stones, and the gold setting is often worth more than the stone.
How to check yours, step by step
- Look for color zoning. Hold the stone against a white card in daylight and look through the side with a 10x loupe. Natural amethyst almost always shows color that is not even: straight-edged bands, V-shaped chevrons, or a darker tip and paler base. The zones have angular, geometric edges because they follow the crystal faces as it grew. Even color from every angle is a sign of glass or, less often, synthetic.
- Hunt for bubbles. Tilt the stone slowly under a lamp. Round, perfectly spherical bubbles, sometimes in strings or clouds, mean glass. Amethyst has inclusions too, but they look different: fingerprint-like healed fractures, needle-like crystals, flat liquid-filled veils, and a pattern called tiger stripes or zebra stripes, which are fine parallel lines from twinning. If you see anything round and hollow, stop; it is glass.
- Check the flash. Amethyst is weakly dichroic. Turn a faceted stone slowly and the purple shifts between a slightly reddish purple and a slightly bluish one. It is subtle, and a cheap dichroscope from a gem supply store makes it obvious. Glass shows no change at all because it is not a crystal.
- Do the cool test. Touch the stone to your lip or the inside of your wrist. Quartz pulls heat away and feels cool for a second or two. Glass and plastic feel closer to room temperature. A quick screen, not a verdict; a small stone in a warm ring never feels cold.
- Scratch glass with it. Amethyst is quartz, hardness 7 on the Mohs scale. Glass is about 5.5. Drag a corner of the stone across a glass bottle or a scrap window pane; quartz leaves a scratch, glass does not. Never scratch the stone itself, and never test a stone on a setting you cannot replace.
- Look at the facet edges. Under the loupe, a worn amethyst still has crisp facet junctions. Glass that has been worn for a few years shows rounded edges, chips at the corners and tiny conchoidal (shell-shaped) nicks, because it is softer and more brittle.
- Read the setting. Gold and platinum settings tell you something about the stone, because jewelers rarely set glass in 18k gold. Check the inside of the band or the back of the pendant for a mark such as 14K, 585, 18K, 750, 925 or PLAT; our guide to how to read jewelry hallmarks explains them. Costume jewelry with purple stones in base metal is nearly always glass, and that is fine; it was never sold as amethyst.
- Consider heat and origin. Most citrine on the market is amethyst heated to about 400 to 500 degrees Celsius, which turns it yellow or orange. Green quartz sold as prasiolite is the same thing heated or irradiated from certain deposits. A pale, slightly brownish amethyst may also have been gently heated to lighten it, which is accepted practice and does not affect price. None of this is detectable at home, and none of it makes the stone fake.
What amethyst sells for
Amethyst is abundant. Brazil, Uruguay, Zambia and Bolivia produce it by the ton, and a single Uruguayan geode can hold thousands of carats of cuttable material. That keeps the price low at every grade except the very top. The figures below are retail and resale ranges for loose stones and finished jewelry as of late 2026.
| What you have | Typical value, about | Notes |
|---|---|---|
| Commercial amethyst, pale to medium, any size | $2-10 per carat | Most jewelry store amethyst; large sizes do not add much per carat |
| Good medium-dark, well cut, eye clean | $10-25 per carat | Zambian and Uruguayan stones; clean, bright, no visible zoning face up |
| Siberian color: deep purple with red and blue flashes | $20-60 per carat | The top grade; mostly from Uruguay and old Russian material today |
| Synthetic amethyst, any grade | $1-3 per carat | Common in mass-market jewelry; honest sellers label it |
| Purple glass or plastic | A few cents | Costume jewelry; the setting carries whatever value there is |
| Amethyst geode or cluster, hand-sized | $15-80 | Sold by weight and color depth; chipped points lower the price |
| Amethyst cathedral geode, 2 to 4 feet tall | $500-5,000 | Depth of color, uniform crystals and a clean rim set the price |
| Victorian amethyst brooch or pendant in 9k to 15k gold | $200-900 | Value is mostly the gold and the period work; the stone adds a little |
| Modern amethyst ring, 14k gold, 2 to 5 carat stone | $150-500 | Resale; the gold content is about half of it |
| Amethyst strand, graduated beads, 16 to 18 inches | $20-150 | Beads are cut from lower-grade rough; dyed quartz and glass are common |
The clearest way to see where the money is: a 3 carat medium amethyst in a 14k ring holds about $15-40 of stone, while the ring's 4 grams of 14k gold hold about $280-300 of metal at a gold price of about $4,000 per ounce as of late 2026. The gold matters more than the stone in most inherited amethyst jewelry, which is why our guide to how to tell if gold is real is the next thing to read.
Natural, synthetic, glass: a side by side
| Point | Natural amethyst | Synthetic amethyst | Glass |
|---|---|---|---|
| Color distribution | Angular zoning, chevrons, uneven depth | Usually very even; sometimes a flat seed plate line | Perfectly even, or swirled streaks |
| Inclusions | Fingerprints, needles, tiger stripes, liquid veils | Mostly clean; rare breadcrumb-like specks | Round bubbles, swirls |
| Dichroism | Weak reddish to bluish purple | Same as natural | None |
| Hardness | 7, scratches glass | 7, scratches glass | About 5.5, scratched by quartz |
| Feel | Cool | Cool | Closer to room temperature |
| Facet wear | Crisp edges | Crisp edges | Rounded edges, chips |
| Common in | Fine and mid-range jewelry, geodes | Mass-market jewelry since the 1970s | Costume jewelry, antique paste |
| Price, about | $2-60 per carat | $1-3 per carat | Cents |
Synthetic amethyst is the awkward case. It is grown hydrothermally from real quartz, so every physical test matches natural. Gem labs separate the two using infrared spectroscopy and by finding twinning that synthetic stones lack, and even then some stones come back as undetermined. Because the price gap is small, most labs charge more for the report than a typical amethyst is worth, so the test is reserved for large, fine stones and for pieces where a seller claimed a specific origin.
Amethyst versus the stones it gets mistaken for
Purple is a crowded color. Iolite is a bluish violet with much stronger dichroism, strong enough to look almost colorless from one direction. Purple sapphire is far harder (9), brighter and worth many times more; a stone sold as amethyst that turns out to be sapphire is a pleasant surprise, and our guide to how to tell if a sapphire is real covers that check. Purple fluorite is softer (4), often shows cubic cleavage cracks and feels heavier. Tanzanite is blue-violet and much more expensive. Ametrine is amethyst and citrine in one crystal, purple on one side and yellow on the other, from a single mine in Bolivia; it is real amethyst and sells for about $5-20 per carat.
How WorthPic reads amethyst photos
WorthPic runs on the newest and most capable AI model available, tuned for exactly this kind of identification. Send a photo of the stone face up in daylight, a close shot through the side against a white background, and the setting with any marks, and it reads the depth and evenness of the purple, whether zoning or inclusions are visible at the resolution of the photo, the cut quality and facet condition, and the metal and marks on the mount. From that it estimates the carat weight from the dimensions, places the stone in a grade, reads the setting against the gold price and gives an honest value range for the piece as a whole, with the stone and the metal weighed separately. It says plainly when the photo cannot show something, which with amethyst is usually the difference between natural and synthetic, and sometimes between a dark amethyst and a purple sapphire or glass in a small stone, and it names the photo that would help, usually a backlit close-up through the side. It identifies and estimates. It never authenticates a stone, never issues a lab report and never vouches for origin; a gem lab with the stone in hand is what settles the question for any amethyst worth more than a few hundred dollars.
Common mistakes
- Treating even, flawless color as a sign of quality. In amethyst, perfectly even color in a large stone points to synthetic more often than to a rare natural.
- Assuming a dark stone is worth a lot. Very dark amethyst goes black in low light and is valued below a bright medium-dark stone with good flash.
- Pricing by carat weight alone. Amethyst does not climb steeply with size the way sapphire and diamond do; a 20 carat stone is still a few dollars per carat at commercial grade.
- Calling heated amethyst fake. Heating to produce citrine or to lighten color is standard and disclosed in the trade; the stone is still quartz.
- Mistaking a purple glass stone in an old gold brooch for a worthless piece. The brooch may be 15k gold and Victorian; the glass was often the fashion of the time.
- Scratching the stone to test it. Scratch glass with the stone, never the other way around, and never on a stone you may want to sell.
What to photograph
- The stone face up in daylight on a white card, which shows the true color and whether zoning is visible face up.
- A close-up through the side of the stone, backlit by a window or a lamp behind a sheet of paper, which is the photo that shows zoning, bubbles and inclusions and settles glass against quartz.
- The pavilion (back) of the stone if the setting is open, where zoning and the seed plate of a synthetic are easiest to see.
- Any mark inside the band or on the back of the mount, close enough to read.
- The whole piece on a plain background with a ruler or a coin for scale, so the stone size can be estimated.
- Facet edges and the girdle close up, to show wear.
When to get it looked at in person
- A gem lab such as GIA, AGL, SSEF or Gübelin issues a report on identity and whether a stone is natural or synthetic. Expect about $50-150 for a small stone. Worth it only for large, fine-color stones, for stones sold with an origin claim, and for anything over about $500.
- A jeweler with a refractometer and a dichroscope can confirm quartz in a few minutes, which is enough for most pieces. A jeweler with an XRF analyzer also reads the gold content of the setting, which is often where the value is.
- An appraiser or auction house jewelry specialist for antique pieces, where the period, the maker and the gold matter more than the amethyst. Our guide to how to tell if a ring is antique covers what to look for first.