The three kinds of fake
French Wikipedia's article on fake minerals and fossils sorts them into three families, and the split is useful when you shop:
- A real stone transformed: heated to change colour (amethyst turned into 'citrine'), dyed (agate, quartz coated with metal), irradiated, glued (loose crystals fixed onto a bare matrix, or broken crystals reattached).
- Something made: glass or resin crystals, pottery geodes, fake fossils built from shell fragments in sand and cement.
- A naming game: an old or misleading name for a cheaper stone, such as 'Bohemian topaz' for citrine, chrysocolla sold as turquoise, or pyrite sold as a gold nugget.
The most commonly faked crystals
These come up again and again:
| Sold as | Often actually | How to check |
|---|---|---|
| Citrine | Heat-treated amethyst | Orange to brownish colour, often as clusters or geode pieces; natural citrine is pale yellow |
| Opalite, 'sea opal' | Synthetic glass | Blue on a dark background, milky with an orange glow on a light one; may show air bubbles |
| Turquoise | Dyed howlite or magnesite | Colour concentrated in cracks and grain boundaries; very uniform veining |
| Brightly coloured geodes | Dyed quartz geodes | Electric blue, hot pink or neon green do not form naturally |
| 'Aura' quartz | Quartz coated with metal | Rainbow surface film that can scratch off |
| Large crystal at a low price | Glass or resin | Feels warm and light, mould lines, bubbles, identical copies |
Moroccan fakes to watch for
Morocco produces superb natural minerals and fossils, and also some of the best-known fakes, because both are sold in large numbers to visitors. French Wikipedia notes that fake-making there is still largely a craft. The usual suspects:
- Galena 'geodes': a pottery shell studded with match ends, coated so that metallic points form, then painted black outside and white on the rim. Natural galena forms cubes and octahedra.
- Glued vanadinite: loose red crystals glued onto barite they never grew on, or crystals reattached after mining. Look at the base of each crystal with a loupe.
- Oiled or varnished pieces: when the matrix shines as much as the crystals, the piece is coated.
- Trilobite casts and composites: resin copies, or real parts of several animals assembled into one. Composite fossils are common across the fossil trade.
- Carved 'orthoceras' plates: real fossil limestone, but cones deepened or added to look richer.
Seven checks you can do yourself
None of these is proof on its own; together they catch most fakes.
- Price: a large perfect crystal far below the going rate is the first warning. Compare with the price data in our mineral guides.
- Temperature and weight: glass and resin feel warm and light; most crystals feel cool and dense.
- Bubbles and swirls: round bubbles and flow lines point to glass or resin. Natural inclusions are irregular.
- Colour in cracks: dye pools in fractures and along grain boundaries.
- Repetition: identical shapes across many listings suggest a mould.
- Loupe at the joins: a glue line or shiny rim where crystal meets rock.
- UV torch: some glues and resins glow differently from the stone. A hint, not proof.
What an honest seller tells you
Repairs and treatments are not always a problem. A broken crystal glued back in place, a polished fossil or a heated stone can be fine to buy, at the right price, if it is disclosed. Ask for the exact locality, photos of the back and sides, and a written statement of any repair, treatment or restoration. A seller who refuses is the answer.
Questions collectors ask
What crystals are commonly faked?
Citrine (heated amethyst), opal and moonstone (opalite glass), turquoise (dyed howlite or magnesite), brightly coloured geodes (dyed), and in Morocco galena geodes, trilobites and glued vanadinite.
How can I tell if a crystal is real at home?
Check the price, temperature and weight, look for bubbles and mould lines, check whether colour pools in cracks, and inspect joins with a loupe. Several warnings together are a strong sign.
Is heat-treated citrine fake?
It is real quartz, but it was amethyst before heating. It should be sold as heat-treated.
Are Moroccan fossils real?
Many are, but casts, composites and undisclosed restorations are common. Ask for the species, locality and a written restoration statement.
Sources
- Wikipédia, Faux minéraux et fossiles (types of fakes, Morocco)
- Wikipédia, Galène (fake galena geodes)
- Wikipedia, Citrine (heat-treated amethyst)
- Wikipedia, Opalite (synthetic glass)
- Wikipedia, Turquoise (dyed howlite and magnesite imitations)
- Wikipedia, Geode (dyed geodes)
- Wikipedia, Fossil trade (composites)