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What Is Fool's Gold?

Author:

K S Lane is a student of science and is deeply passionate about educating others on her favourite topics.

Fools gold, chemical name pyrite, is a shiny brass-coloured mineral that almost perfectly mimics the look of gold. The differences between the two metals, however, are significant. Fools gold isn’t nearly as valuable as gold because of its differing properties, so if you’ve found a gold, metallic rock in your backyard don’t rejoice just yet. However, if your miracle find does turn out to be plain old pyrite it’s not all bad news, because fool’s gold has it’s own unique uses and can also indicate the presence of other precious metals in the vicinity. You’d be a fool discount its importance completely!

Fool's gold, or pyrite, is a shiny, brassy coloured mineral that's often mistaken for true gold.

Fool's gold, or pyrite, is a shiny, brassy coloured mineral that's often mistaken for true gold.

A Brief History of Fool's Gold

Fool’s gold earned its name from early miners, who’d find the gold-like rock in their pans and mine shafts and mistakenly think they’d just scored a fortune. The mineral was initially hated by prospectors, who associated it with only crushing disappointment, until it was found that pyrite has a value of its own. After this was discovered fool’s gold became an incentive for many early European explorers to journey to North America and cart back the mineral by the ton to Great Britain and France for a profit. This boom eventually died down and pyrite went back to being relatively useless, until the early 1900s when Lawrence Bragg used a sample of the mineral to conduct some of the earliest research on crystalline structures.

Early prospectors coined the name 'fool's gold' as the inexperienced were often tricked into thinking that the pyrite they found in abundance was actually gold.

Early prospectors coined the name 'fool's gold' as the inexperienced were often tricked into thinking that the pyrite they found in abundance was actually gold.

What is Pyrite?

Pyrite is a mineral composed of iron and sulphur. Given that iron has a shiny sheen and sulphur is a brassy yellow colour, it’s clear how the mineral often gets mistaken for gold. Pure pyrite has the chemical formula FeS2 and is the most abundant sulphide mineral on earth. Deposits of the crystal are found all over the world, in sedimentary rocks such as limestone and shale, metamorphic rocks like schist and in hydrothermal veins.

Pyrite is comprised of iron (Fe) and sulphur (S) and often forms cuboidal crystals, as pictured above.

Pyrite is comprised of iron (Fe) and sulphur (S) and often forms cuboidal crystals, as pictured above.

What's the Difference Between Pyrite and Gold?

Upon first inspection, you should be able to tell that miracle lump of 'gold' is pyrite if it feels light in your hands and if the surface can’t be scratched, either with your fingernail or with a pocket knife. This is because pyrite is much harder than the notoriously soft and malleable gold. If you want to conduct further tests, try crushing a bit of your find. Pyrite will crumble into a greenish-black powder, while gold power still retains it’s golden colour. Pyrite is also far more brittle than true gold so if you can snap the lump in half you’re not going to be a millionaire today. Sorry.

GoldPyrite

Soft and malleable

Hard and brittle

Forms a yellow powder when crushed

Forms a black/green powder when crushed

Worth about $1300 per ounce

Worth about $35 per ounce

What are Pyrite's Uses?

Though it’s not as precious gold, pyrite still has plenty of uses. During World War Two the mineral was actively mined for its sulphur content in order to produce sulphuric acid. Today, pyrite can be used as a gold substitute in making jewellery and is also used in some car batteries. Some pyrite deposits can also contain up to 0.25% gold by mass and can thus be broken down to extract the more lucrative metal. When struck together, lumps of the mineral can produce a spark the can be used for lighting fires, hence the inclusion of pyr- (greek: fire) in the name. Because of this, fool’s gold is occasionally used in flintlock firearms. On a more modern scale, pyrite has been found to have semi-conductive properties and is currently being investigated as a potential material to make solar cells from. Fool’s gold can also be a sign that a deposit of real gold or even copper may be close by, and can thus be used as a kind of indicator for prospectors when they’re deciding where they should be mining.

Pyrite has a number of diverse uses, including in the production of sulphuric acid, in jewellery and as a potential candidate for new solar cells

Pyrite has a number of diverse uses, including in the production of sulphuric acid, in jewellery and as a potential candidate for new solar cells

In Summation:

Fool’s gold is a relatively common mineral that, unfortunately, isn’t as valuable as gold. To the untrained eye the two substances can seem identical, but pyrite is actually much harder and more brittle than gold and forms a black/green powder when crushed. However, if you’ve discovered a deposit of fool’s gold in your backyard don’’t despair just yet, because the mineral has its own uses and can also indicate that a deposit of cooper or true gold is close by.

Were you paying attention ?

For each question, choose the best answer. The answer key is below.

  1. What is the chemical formula of pyrite?
    • Fe2S
    • FeS2
    • Fe2S2
    • Pyr
  2. When pyrite is crushed what colour powder does it form?
    • Golden
    • Brown
    • Green/black
  3. Pyrite is sometimes used in what kind of firearm?
    • Automatic weapons
    • Pistols
    • Flintlock
  4. What scientist used pyrite to research crystalline structures?
    • Frances Crick
    • Jonas Salk
    • Lawrence Bragg
  5. Deposits of pyrite can be found in what type of rock?
    • Metamorphic rocks
    • Sedimentary rocks
    • Hydrothermal vents
    • All three
  6. In World War II pyrite was used to...?
    • Power weapons
    • Extract iron
    • Produce sulphuric acid
  7. Pyrite deposits have been found to contain up to what percentage of gold?
    • 0.25%
    • 0.70%
    • 25%
    • 5%

Answer Key

  1. FeS2
  2. Green/black
  3. Flintlock
  4. Lawrence Bragg
  5. All three
  6. Produce sulphuric acid
  7. 0.25%

Sources and further reading:

Questions & Answers

Question: Can you turn pyrite into gold?

Answer: It would be great if you could but, unfortunately, the answer is no. Pyrite is a completely different substance to gold and while the ancient alchemists might disagree, modern science dictates that minerals can't just be turned into gold at will.

© 2018 K S Lane

Comments

Jessie Watson from Wenatchee Washington on May 11, 2018:

I wouldn't know much about actual gold prospecting but it's a blast. I live in eastern Washington and we have creekbeds chaulked full of pyrite flakes.

There's also a land mass near me called "Saddle Rock" which is purported to have the worlds largest reservoir of gold underneath. I have yet to confirm that.

K S Lane (author) from Melbourne, Australia on May 11, 2018:

Jessie- sounds like a great way to teach kids about prospecting!

Jessie Watson from Wenatchee Washington on May 11, 2018:

It's fun to take children to creeks and rivers that are rich in pyrite particulates and "gold pan".

K S Lane (author) from Melbourne, Australia on May 10, 2018:

Nell- I find it fascinating, too. Diamonds are worth millions and graphite is worth basically nothing, but they're made of exactly the same thing! Humans are strange creatures.

Nell Rose from England on May 10, 2018:

How interesting! I had heard of it, but didn't know what it was before. Its strange how we have defined different rocks over the centuries, one is worth thousands, the other nothing. I know there is lots of it, but...

Great hub!