Currency…what makes gold…golden?

Humankind’s attitude to gold is bizarre. Chemically, it is uninteresting – it barely reacts with any other element. Yet, of all the 118 elements in the periodic table, gold is the one we humans have always tended to choose to use as currency. Why?  Why not osmium or chromium, or helium, say – or maybe seaborgium?

Well, let’s go through a process of elimination:

We can immediately eliminate the right-hand side of the table – noble gases and halogens wouldn’t be very practical to use as currency.

Periodic Table of the Elements

The two liquid elements – mercury and bromine – are poisonous – not a good quality in something you plan to use as money. Similarly, we can cross out arsenic and several others.

On the left-hand side of the table, the alkaline metals and earths are just too reactive (remember the fizzy chaos of dropping sodium or potassium into a dish of water in high school?).  A similar argument applies to another whole class of elements, the radioactive ones: you don’t want your cash to give you cancer.  Out go thorium, uranium and plutonium, along with a whole bestiary of synthetically-created elements – rutherfordium, seaborgium, ununpentium, einsteinium – which only ever exist momentarily as part of a lab experiment, before radioactively decomposing.

Then there’s the group called “rare earths”, most of which are actually less rare than gold.  Unfortunately, they are chemically hard to distinguish from each other, so you would never know what you had in your pocket.

This leaves us with the middle area of the periodic table, the “transition” and “post-transition” metals.  We’ve got some very tough and durable elements – titanium and zirconium, for example, but they are very hard to smelt.  The specialist equipment required wasn’t available to ancient civilisations. Aluminium is also hard to extract, and it’s just too flimsy for coinage. Most of the others in the group aren’t stable – they corrode if exposed to water or oxidise in the air.

So, what’s left?

Of the 118 elements, we are now down to just eight: platinum, palladium, rhodium, iridium, osmium and ruthenium, along with gold and silver.  These are known as the “noble” metals because they stand apart, barely reacting with the other elements.  They are also all rare, another important criterion for a currency.

But all the noble metals except silver and gold are so rare that you would have to cast some very tiny coins, which you might easily lose.  They are also hard to extract.

That leaves silver and gold.

Both are scarce but not impossibly rare.  Both also have a relatively low melting point and are therefore easy to turn into coins or jewellery.

Silver tarnishes – it reacts with minute amounts of sulphur in the air. That’s why we place a particular value on gold.

It turns out then, that the reason gold is precious is precisely that it is so chemically uninteresting. Gold’s relative inertness means it doesn’t lose its looks, even after thousands of years.

So what does this process of elemental elimination tell us about what makes a good currency?

Firstly, it doesn’t have to have any intrinsic value.  A currency only has value because we, as a society, decide that it does.  It also needs to be stable, portable and non-toxic.  And it needs to be fairly rare – you might be surprised just how little gold there is in the world (it’s guesstimated that all the gold in the world would form one 20 metre cube).

But gold has one other quality that makes it the stand-out contender for currency in the periodic table. Gold is… golden.  All the other metals in the periodic table are silvery-coloured except for copper – but copper corrodes, turning green when exposed to moist air. That makes gold very distinctive.  

And, of course, gold is beautiful, which is perhaps the most powerful driver of all.

You can read further lighter side articles here.

Pamela Hellig