How to tell real turquoise from fake
Hardness separates turquoise from five of its six common substitutes and density from five. Faustite defeats both, and it is not a fake but a valid species.
Turquoise is a copper aluminium phosphate, hardness 5 to 6 and density 2.86. A steel point separates it from five of the six minerals traded as turquoise, and a density measurement separates five — but magnesite at 3.00 is denser, not lighter, so heft points the wrong way. Faustite, at hardness 5.5 and density 2.92, defeats both tests on every specimen and is a valid species rather than a fake.
In short
- Scratch before you weigh. Hardness separates turquoise from howlite, magnesite, variscite, chrysocolla and dyed chalcedony. Density separates the same five but gets magnesite backwards, because magnesite is the denser mineral.
- Magnesite is the substitute the standard advice misses. At density 3.00 against turquoise's 2.86 it is heavier, not lighter, so “real turquoise feels heavy” is advice that fails on the commonest dyed substitute in the trade.
- Faustite is the honest hole in both tests. Hardness 5.5, density 2.92, and it is the zinc analogue of turquoise on the IMA list — a genuine species in the turquoise group, not a counterfeit. Nothing you can do at home separates it.
- Dyed chalcedony fails the scratch test in the other direction. Quartz is hardness 7, so a steel point slides off it where it bites turquoise. A stone that resists steel is not turquoise, whatever colour it is.
- Most “fake turquoise” is a real mineral that has been dyed — a crust, a crystal or a cut stone of a genuine species, not a plastic. That matters, because the tests that work are mineralogical ones on the host material rather than anything aimed at detecting the dye.
| Material | Hardness | Density | Caught by a steel point? | Caught by weighing? |
|---|---|---|---|---|
| Turquoise, CuAl6(PO4)4(OH)8(H2O)4 | 5 to 6 | 2.86 | — | — |
| Howlite, dyed | 3.5 | 2.53 to 2.59 | Yes — marks easily | Yes — clearly lighter |
| Magnesite, dyed | 3.5 to 4.5 | 3.00 | Yes — marks | Yes, but it is heavier |
| Variscite | 4.5 | 2.57 to 2.61 | Yes — marginally | Yes — lighter |
| Chrysocolla | About 2 to 4 | 1.93 to 2.4 | Yes — marks very easily | Yes — much lighter |
| Chalcedony, dyed | 7 | 2.65 | Yes — steel slides off | Marginally — a 0.21 gap |
| Faustite, ZnAl6(PO4)4(OH)8(H2O)4 | 5.5 | 2.92 | No | No |
Why I should scratch before I weigh
The advice a collector usually meets is that real turquoise feels heavy for its size. Set the actual numbers out and that advice falls over on the commonest substitute in the trade.
The Handbook of Mineralogy gives turquoise a measured density of 2.86 and magnesite 3.00. Dyed magnesite is denser than the turquoise it is imitating. A buyer applying the heft rule to a magnesite bead rejects the real stone and keeps the substitute.
Hardness does not have that failure. Turquoise is 5 to 6; magnesite is 3.5 to 4.5, howlite 3.5, variscite 4.5, chrysocolla about 2 to 4. A steel point at roughly 5.5 bites all four and struggles on turquoise. Every substitute that hardness catches, it catches in the right direction — softer, with one exception that is just as informative, below.
So the order is: hardness first, density second as a confirmation, and both interpreted against the specific substitute rather than against a general rule. Our note on testing hardness properly covers doing this without leaving a mark you regret — the short version is to test on an inconspicuous edge, wipe the track, and check whether you cut the stone or merely left steel on it.
The exception that runs the other way: dyed chalcedony
Dyed chalcedony — sold as turquoise, or as “turquoise howlite”, or under a trade name — is quartz, at hardness 7 and density 2.65.
It is the one substitute that is harder than turquoise, not softer. Draw a steel point across it and the point slides, leaving a grey metal smear that wipes away, because nothing steel can do marks quartz. Do the same on turquoise and it bites.
That makes the scratch test a two-sided instrument rather than a one-sided one. A stone that marks easily is not turquoise, and a stone that resists steel completely is not turquoise either. Turquoise sits in the narrow middle where a steel point marks it with difficulty, and learning what that feels like on a known specimen is worth more than any amount of reading.
Density is weaker here — 2.65 against 2.86 is a gap of 0.21, which needs a careful hydrostatic weighing rather than an impression in the hand. Our note on measuring specific gravity at home shows what specimen size that demands.
Faustite, and the honest limit of what these tests can do
There is one material in the group that neither test resolves, and this page would be dishonest if it stopped before saying so.
Faustite is hardness 5.5 and density 2.92, against turquoise's 5 to 6 and 2.86. The hardness sits inside turquoise's range and the density is 0.06 away — well inside the error of any measurement a collector can make at home, and well inside the natural variation of porous turquoise itself.
It is also not a fake. The IMA-CNMNC master list carries faustite as a valid species first described from the USA in 1953, with the formula ZnAl6(PO4)4(OH)8(H2O)4 — turquoise with zinc where turquoise has copper. It is a member of the turquoise group, it forms in the same settings, and it is apple-green rather than sky-blue, which is the only clue available without analysis.
So the honest position is: greenish material in the turquoise colour range cannot be settled at home, and blue material in the same range usually can. That is a narrower claim than most guides make and it is the one the numbers support. Our note on turquoise as a species covers the mineralogy; this page covers what you can act on.
Stabilised, reconstituted and dyed — three different things
Substitution is only half the market. The other half is turquoise that is genuinely turquoise and has been treated, and the words for it are used loosely enough to be worth pinning down.
Stabilised turquoise is real turquoise impregnated with resin to harden it and stop the colour changing. Most commercial turquoise is stabilised, because untreated material of usable hardness is scarce. Reconstituted or block turquoise is powdered turquoise — sometimes with other material — bound with resin and pressed. Dyed covers both real turquoise whose colour has been deepened and a substitute mineral coloured to imitate it.
The physical tests on this page do not distinguish these, because the host mineral is turquoise in the first two cases. What does is where the colour sits: dye concentrates in cracks, veining and porous zones, and stops abruptly at a polished surface. Our note on telling whether a crystal is dyed works through that in detail, and our note on fake crystals covers the wider market.
What it costs to do this properly. A steel point costs nothing and a scale reading to a hundredth of a gram is inexpensive, but neither is usable on a mounted cabochon or a strung bead, which is the form most turquoise is bought in. On those, you are relying on the seller's disclosure and on where the colour sits. That is the real reason mineral specimens with old locality labels are easier to assess than jewellery: our collecting notes come back to this repeatedly, and our wanted list sets out the documentation that makes a specimen assessable at all.