Quick answer
These checks sort a suspect stone into one of three answers, and the difference matters: glass, resin and plastic are not crystals at all, while a dyed or heat-treated stone is a genuine mineral that has been altered. No home test - including the ones here - can confirm a stone identity. If the piece matters, a gemologist with a refractometer settles it in minutes.
Tick everything you have actually observed. The checker weights each sign, explains what it does and does not prove, and returns a likelihood rather than a verdict. It deliberately will not tell you that your stone is real or fake.
What have you noticed?
The three possible answers
Almost every guide to spotting fakes stops at one answer, and that is where it goes wrong. There are three, and they call for different responses. The first is that the piece is not a crystal at all: glass, resin or plastic, which the touch, weight, bubble and mold-line checks catch reliably. The second is that the piece is a real mineral that has been treated - dyed agate sold as amethyst, amethyst heated into citrine, emerald that has been oiled or filled. The third is that the stone may be fine and the seller is the problem, which is a risk question rather than a material one. The five home tests in our real vs fake guide catch the first group. They cannot catch the second, which is why the tests below are split by what they actually prove.
| What you notice | What it points to | Why | What to do next |
|---|---|---|---|
| It warms up in my hand within a second or two | Not a natural crystal (glass, resin or plastic) | Real stone pulls heat away from skin quickly and stays cool for a moment, like a marble countertop. Resin and plastic warm almost instantly. Glass also stays cool, so this sign points at resin and plastic more than at glass. | Hold it against the inside of your wrist for ten seconds beside a stone you trust. The difference is easier to feel than to describe. |
| It feels light, almost hollow, for its size | Not a natural crystal (glass, resin or plastic) | Quartz has a specific gravity near 2.65, so a real crystal feels heavier than it looks. Glass is a little lighter; resin is dramatically lighter again. | Compare it in each hand against a real stone of similar size rather than judging weight on its own. |
| I can see round, uniform bubbles inside | Not a natural crystal (glass, resin or plastic) | Air bubbles are the classic glass signature. They are round because glass melted and trapped gas. Natural inclusions are irregular, wispy or angular, never neat spheres. | Hold it to a bright light and look for a second bubble. One is possible in a natural stone; a scatter of round ones is not. |
| There is a seam or a mold line, and the edges are rounded | Not a natural crystal (glass, resin or plastic) | Cast glass and resin come out of a two-part mold, which leaves a seam. Real carved stone keeps crisp edges because the material is hard enough to hold them. | Run a fingernail along the edge and look for the crisp, slightly matte facets that cut stone has. |
| It is completely flawless with perfectly even colour, and it was cheap | Not a natural crystal (glass, resin or plastic) | A flawless stone at a low price is almost always glass, which melts into a uniform blob with no internal structure. Natural crystal nearly always shows growth - tiny fractures, veils, mineral specks or colour banding. | Look at it under a bright light from the side. If you can find no internal structure at all, treat that as information. |
| Light passes through it like a window | Not a natural crystal (glass, resin or plastic) | Natural quartz is slightly translucent but never clear like glass - light spreads softly through it. Glass passes light almost perfectly, and resin blocks it almost completely. | Hold a known-real stone next to it in a dim room and compare how much light each lets through. |
| The price is far below what this stone normally costs | Not a natural crystal (glass, resin or plastic) | Amethyst, rose quartz and tiger eye are affordable, and a fair bracelet still runs roughly $20-60. Raw material and handwork have a floor: below it, you are looking at glass, dyed stone or plastic. | Check the range for that stone in our price guide before deciding the deal is real. |
| A knife tip leaves a mark on a hidden edge | Not a natural crystal (glass, resin or plastic) | Quartz ranks 7 on the Mohs scale, so a steel knife does not scratch it. A mark means the stone is softer than steel, which points to glass, calcite or plastic. | Only ever do this on an unpolished hidden edge. Testing a polished surface ruins the finish and proves nothing new. |
| Colour is concentrated in cracks and drill holes, and looks neon-bright overall | A real mineral, but treated, dyed or filled | Dye gathers in the low points. Even, unnaturally bright colour with darker lines in the crevices is the signature of a dyed stone - which is still a real mineral, just not the colour it appears to be. | Rub a hidden spot with a cotton pad dipped in nail-polish remover. Dye comes off on the pad; natural colour does not. This is the one test that separates dyed from natural. |
| The colour is an even, saturated orange, sold as citrine | A real mineral, but treated, dyed or filled | Most citrine on the market is amethyst heated past about 470C. The stone is still a genuine mineral, but it is not natural citrine, and the price should reflect that. | Look for pale, uneven colour - natural citrine is rare, muted and usually more expensive than the bright heated material. |
| It is an emerald or a ruby, and nothing was said about treatments | A real mineral, but treated, dyed or filled | Emerald oiling and ruby glass filling are routine in the trade. The stones are real; the question is what has been done to them, because that sets the price. | Ask directly whether the stone is oiled, resin-filled or glass-filled, and get the answer in writing before paying. |
| The seller uses stock photos, cannot name an origin, and will not discuss treatments | Nothing about the stone - it is a risk signal about the seller | This is not evidence about the stone, it is evidence about the risk. All five home tests are easier to run when the seller gives you real photographs and a straight answer. | Ask for a daylight photo of the actual piece, the bead diameter, and the treatment status in one message. Sellers who answer all three are the better risk even at a slightly higher price. |
What no home test can do
Hardness, weight, temperature and light behaviour identify a material family, not a species. Glass passes for quartz on temperature and often on scratch behaviour. Heated amethyst is amethyst. A home test can tell you a stone is not plastic; it cannot tell you it is the stone you paid for. Where identity genuinely matters - anything over roughly $100, or a stone sold as rare - a lab report is the only answer, and a certificate on a $30 common-quartz bracelet is marketing rather than information.
Sources
- Mohs hardness scale as published in mineralogy references; values cross-checked against species data maintained by Mindat, the mineral database of the Hudson Institute of Mineralogy.
- Treatment and disclosure practice follows the terminology used by the Gemological Institute of America in its gem-treatment guidance.
- Stone identification limits: hardness testing, specific gravity and refractive index are the standard tests, described in the GIA Gem Encyclopedia.
- Identification limits and the role of refractive index, specific gravity and magnification follow the GIA Gem Encyclopedia.
- Heat-treatment temperatures and the amethyst-to-citrine conversion are standard trade practice reported by the GIA.
Disclaimer
This is reference information for buying, wearing and caring for stones, not a laboratory identification and not medical advice. Hardness values follow standard mineralogy and a given piece can behave differently if it is treated, fractured or unusually thin. For anything you intend to put in your mouth, on broken skin or in a container of drinking water, treat a jeweller's or a mineralogist's in-person assessment as the only reliable answer.
