Gold vs pyrite: 7 simple tests to tell them apart
Pyrite shines so brightly that for centuries it fooled prospectors all over the world, which is how it earned the name “fool’s gold”. The good news is that telling them apart is easy once you know what to look for.
What pyrite is and why it gets mistaken for gold
Pyrite is an iron sulphide (FeS2) and one of the most common minerals in the Earth’s crust. It has a metallic lustre and a brassy yellow colour that, at first glance and in good light, looks like gold. Its name comes from the Greek pyr, “fire”, because it throws sparks when struck with steel.
Gold, on the other hand, is a chemical element that occurs in nature almost pure, alloyed mainly with a little silver. The two share a shine, and sometimes even a deposit, but in almost everything else they are opposites. These are the seven tests we use to tell them apart.
1. Colour and shine
Gold has a warm, buttery yellow that stays the same when you turn the piece or move it into the shade. Pyrite is paler, closer to brass and sometimes greenish-grey, and its shine “flickers”: it flashes when the light catches it and goes dull when you turn it. Flakes of mica, another common false gold in river sand, do the same and are also extremely light.
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2. Shape
Pyrite crystallises in geometric shapes: cubes with flat, often striated faces and other forms with straight edges. Spain has one of the most famous localities in the world, Navajún in La Rioja, which produces almost perfect pyrite cubes.
A natural gold nugget has no flat faces or straight edges. It is rounded and irregular, with hollows and folds, and if it comes from a river it is usually polished by the water. If you see a cube, it is not a gold nugget.
3. The streak test
If you rub a mineral on the unglazed back of a porcelain tile, it leaves a streak of powder. Gold leaves a golden yellow streak; pyrite leaves a greenish-black one. It is the classic geologist’s test, but bear in mind that it wears away a little of the piece: don’t do it on a nugget you want to keep.
4. Hardness
Gold is a very soft metal: it has a hardness of 2.5 to 3 on the Mohs scale and a steel needle will mark it. Pyrite is much harder (6 to 6.5) and steel barely scratches it. Again, this is a destructive test: scratching a nugget reduces its value.
5. Malleability
Gold changes shape without breaking, which is why it can be beaten into extremely thin leaf. Press a grain of gold with the tip of a knife and it flattens. Pyrite is brittle: under pressure it breaks into pieces or powder.
6. Weight
This is the clearest difference, and the one that doesn’t damage the piece. Pure gold has a density of 19.3 g/cm³; the natural gold in nuggets, which contains some silver, a little less. Pyrite is around 5 g/cm³. For the same size, a gold nugget weighs almost four times as much as a piece of pyrite.
That is why gold stays at the bottom of the pan while the water carries the sand away, and why a nugget feels heavier in your hand than you expect. With precision scales and a glass of water you can work out the density without harming the piece; we explain how in how to tell if a gold nugget is real.
7. How it ages
Gold does not rust or tarnish: a nugget keeps its colour for centuries. Pyrite, by contrast, can lose its shine in damp conditions, darken and even slowly crumble, because it contains iron and sulphur.
| Gold | Pyrite | |
|---|---|---|
| Colour | Warm yellow in any light | Pale brass, flashes as you turn it |
| Shape | Rounded and irregular | Cubes and flat faces |
| Streak | Yellow | Greenish-black |
| Hardness (Mohs) | 2.5 to 3 | 6 to 6.5 |
| Density | Up to 19.3 g/cm³ | About 5 g/cm³ |
| Under pressure | Bends | Breaks |
What if you are buying one?
If you are buying a nugget, you won’t need to scratch or strike it: just ask for what a good seller always provides. The exact weight in grams, the origin and macro photos of every side showing its natural surface. With that, pyrite or an imitation gives itself away. You will find more advice in where to buy gold nuggets safely.
In our Catawiki auctions every nugget is listed with its exact weight, its origin (Alaska, Australia or Lapland) and macro photos, so you can see exactly what you are buying.
Frequently asked questions
Why is pyrite called “fool’s gold”?
Because its yellow shine fooled many prospectors into thinking they had struck it rich. Weighing or scratching it was enough to find out the truth.
Is pyrite worth anything?
As a collector’s mineral, yes: fine crystals, such as the cubes from Navajún in Spain, are highly prized. But its value has nothing to do with that of gold.
Can gold and pyrite be found together?
Yes. Pyrite often occurs in the same quartz veins as gold, and some pyrite even contains gold that is invisible to the naked eye. That is why prospectors learn to tell them apart early on.
How can I check a nugget without damaging it?
By its weight and density, which you can work out with precision scales and a glass of water. A jeweller or laboratory can also test it with X-ray fluorescence, which does not harm it.
Raquel selects, weighs and photographs every nugget we sell. Gold Nuggets Minerals S.L.U. is a small company in Zaragoza, Spain, specialising in native gold. On Catawiki we have sold more than 120 nuggets, with 100% positive feedback and the Top seller badge.
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