Assuming SHTF does not occur in your lifetime. Now, in the next 10-15 years the semiconductor industry will most likely figure out how to grow industrial quantities of diamonds in their effort to make it into a superior semiconductor. When that happens natural diamonds will still have value, but nothing like right now. Flawless "stones" the size of bird's eggs will not be beyond reach. So scratch diamonds. Besides, can you eyeball a diamond and tell it is real, let alone grade it per GIA? I can't, and that means it has questionable value (glass) to me after SHTF.
Gold: It's starting to get bumpy for price. Nobody knows if it should be going up or down. Which means the market is sideways, screwy and not a good time to be jumping in. If you got in a decade ago, good for you. Now? No way, Jose.
Honestly, I don't think there is a crystal ball out there right now that is more than milky white. Nobody, NOBODY, has a clue where the world is going, least of all the self-proclaimed Prophets. They are just bilking people while they walk around like Zombies.
And that's the real problem: we got Zombies everywhere right now! Zombies in government, just pushing the same paper over and over; Zombies in the voting booths, just pulling the same lever, over and over again. Zombies in the pulpits, preaching the same sermons over and over again. BIG TIME Zombies in Hollywood cranking out re-make after re-make.
Would you trust your life's investments to a stock market Zombie? Would you trust Stock Market regulation to a bunch of Zombie Protesters? Or Zombie News people?
I don't know what the right answer is, but I know a LOT of wrong ones.