Lots of things can be used as currency. Gold was the OG because it is scarce, takes work to mine, is finite(ish), it doesn’t tarnish or corrode in air or salt water, isn’t attacked by acids except agua regia, meaning it doesn’t degade over time. It’s a really good medium for labor-value.

Problem is, it’s also a useful metal now, in semiconductors and electronics, so now it is being ‘consumed’ by industry in a way that isn’t readily recoverable except at product end of life, and even then it’s not 100% recycled, probably more like 10%.

So the global supply increases due to work mining, decreases due to consumption as a commodity, and is still treated as a currency equivalent.

Solid gold is easy to store, and will survive calamities, bank collapses, fires, floods, ect where other intrinsic value items don’t.

So it’s a good investment if you believe that you will survive the deletion of society, AND you believe that it will be tradeable post-collapse. Or if you just treat it like a commodity.

But post-collapse, gold isn’t intrinsically useful. In these events, other useful, consumable goods might be better for goods and labour exchange. In the early Australian colonies, there was no money, people bought, sold and got paid in rum.

Rum is a reasonable value holder, it can be preserved against degrading, it is ‘fungible’ and divisible in a way that gold coins arent.

Dried grains are a good currency too. Maize, wheat berries, etc, as long as you accept that your value will be contually consumed and replenished.

Whether a thing has value is largely determined by whether the society you end up in decides it has value.

The indigenous Australians would happily trade a gold nugget for rum or rope or steel tools, because their society had no use for gold, but did have use for steel.

Disclaimer: The only gold I own is in my phone and computer.