Gold has several key properties that make it ideal for use in coinage, but its scarcity, unlike zinc or nickel, is what makes it inherently valuable. You will probably be amazed by just how little gold is found on earth. All the gold mined from the ground throughout human history would form a cube of only 20.5 meters on a side! I first learned this about 15 years ago, and I am still awestruck by it.

As seen in the infographic above, the cube fits in an Olympic-sized swimming pool (which is 25 m wide and 50 m long). While this beautiful illustration makes plainly obvious how little gold there is, the volume is still *large* enough that we may have some difficulty coming to grips with it. So, I’ve come up with a few examples to help comprehend this small, yet strangely large, volume of gold.

First off, since there’s a swimming pool involved, let’s look at the water and how much we drink. The average American adult drinks in 2.60 liters of water each day (1.06 L of plain water and 1.54 L in other beverages). Over the course of a lifetime, assuming an age of 80 years, this totals nearly 76,000 L. This volume seems impossibly large, but in reality it is only the amount of water in a 9-yard square area of the shallow end of a pool. *So, as you stroll through a 3.5 foot-deep shallow end and mark off a square of about 12 steps a side, that’s all the water you need to drink for a lifetime!* This is obviously far smaller a volume than all the gold ever mined. In fact, that volume of the 20.5 m cube of gold would contain the lifetime water needs of 113 people. Seen another way, that cube contains the daily water needs for 3.3 million Americans.

Well, what about milk? We’re used to the size of a gallon of milk. What sort of liquid volumes are associated with milk consumption and production? The total milk production for an average U.S. cow is given as 9164 kg per year. An average cow has just 3-4 lactation cycles, which is 3.5 to 4.5 years, depending on the rest they’re given, so let’s go with an average of 4 years, meaning 36,656 kg of milk is produced in a lifetime. The density of milk is about 1.03 kg/L, so total volume is 35,590 L (remember a gallon of milk is about 4 L, so that one cow produces about 8900 gallons of milk in a lifetime). This is about half the volume of water a person consumes in a lifetime, and it means the volume of the 20.5 m cube of gold would contain the total lifetime milk production of 242 cows. Looking at the milk a little differently, there are 9,189,000 milk cows in the U.S., which produce 81.8 billion liters of milk a year, meaning* just 55 minutes of milking from all the U.S. cows would fill that cube of gold*.

The other liquid volume we’re used to is gasoline. If you pump gas once a week for your car, maybe 15 gallons (60 L) per fill-up, in 50 years you will pump 156,000 L. *So the 20.5 m cube of gold has the volume for 55 people’s lifetime gas pumping*.

Finally, it makes sense to look at another much more abundant metal, aluminum, and its mining production compared to gold. World-wide aluminum production last year was a staggering 62,616,000 metric tons (6.2616 x 10^{10} kg). With the density of aluminum being 2.70 kg/L, that’s 2.319 x 10^{10} L of aluminum produced each year! *So, 3 hr. and 15 min. of current worldwide aluminum production would produce the same volume as all the gold ever produced!*