While gold in the ground may be hard to quantify, it’s not the only source. There is also gold on the moon.

However, the costs associated with mining it and transporting it back to earth are significantly higher than the value of the gold.

“Whilst it exists, it would never be economically meaningful to mine it,” says space expert Sinead O’Sullivan. “You would lose an infinitely larger amount of money mining it than you would gain by selling it.”

Similarly, there are some known gold deposits in Antarctica that may never be economical to mine, due to the continent’s extreme weather conditions.

Gold is also scattered along the ocean floor, but is also considered uneconomic to mine.

One factor gold has on its side though is that, unlike other non-renewable resources like oil, it can be recycled. So we will never run out of gold, even when we can no longer mine it.

A large amount of gold is used in electronic products that are widely viewed as disposable, such as mobile phones. The amount of gold in the average phone is worth a few pounds.

Efforts to recycle gold extracted from electronic waste are already well under way.