Diamond prices are down 60% since a 2011 high, and they are still falling. It's not all down to lab-grown diamonds, demand is down too, especially in China.
No one can lab-grow gold yet, so its rarity and scarcity protect its value, but that will end too. It's just a question of when. China launched an asteroid touch-down mission this week, which will make it the 4th country/region to do so, after Europe, the US & Japan.
How soon will it be feasible to mine asteroids? Who knows, but a breakthrough in space propulsion might mean the prospect happens quickly when it does. It's possible gold has twenty years or less of being high value left.
The $80 Billion Diamond Market Crash Leaves De Beers Reeling
Why not lab grown gold?
*(it's not a serious question)
Because of nuclear physics.
Diamonds are just carbon atoms arranged in a particular repeating structure (a lattice). So you can go from, say, graphite to diamond without touching the atoms themselves.
Gold, on the other hand is not about structure, but the atomic cores themselves, which contain exactly 79 protons. Going from one type of atom to another type requires some form of fission (breaking larger cores into smaller pieces) or fusion (smashing two smaller cores together). I don't think there are (viable) fission "recipes" that yield gold. And fusion requires insanely high temperatures or pressures even for smaller atoms (were talking center of the sun here).
I fused with your mom last night.
Sigh, I'll go get the chainsaw ...
Cut it out, dad.
Alchemists have been trying for thousands of years, you're welcome to join them
Now we call them nuclear physicists
they actually made gold from lead, in the hadron collider. but it was a few particles, and very unstable, still gold!
Diamonds are just Carbon atoms in Chrystal form.
You can take carbon from say coal, turn it into a Chrystal and you've got a diamond.
Gold is just gold atoms, you can't make gold atoms
Well, you can make gold atoms (see here), but it takes many times more energy per atom because the energy contained in the bonds between neutrons and protons in the nucleous of atoms is many-fold the energy contained in the bonds between atoms (just see the difference in potency of conventional explosives - which release energy contained in the links between atoms - and fission and fusion bombs - which release the energy contained in the bonds within the atomic nucleous) hence it's not really an economic viable way of making gold.