I live in California — specifically in the San Francisco Bay Area, a place whose history is indelibly shaped by the gold rush of 1848. And, having proposed in last week’s essay a speculative path to industrialization involving the discovery of some kind of unobtanium, I find myself led naturally to the notion of a rush: a sudden influx of hopeful miners to the location of a newly discovered mineral deposit, seeking to make their fortunes in one fell swoop.

We hear about these mostly as gold rushes, but they can actually happen for other resources, too; there have been silver rushes and diamond rushes. So what elements are necessary to cause a rush?

First and most obviously, the object of the rush must be highly valuable. Nobody’s going to travel for months, often through rugged wilderness (because all the sites closer to home have already been claimed), to go after an ordinary resource like iron or coal. Or rather, they will, but not in the kind of sudden mass migration that leads us to call such an event a rush. If people don’t grow starry-eyed at the thought of getting their hands on some of that thing, it’s not fancy enough for this scenario. Think especially in terms of value versus volume: something that wows people when you hold it in the palm of your hand will have much more power to attract prospectors than something that requires an entire cartload to impress.

Second, it has to be (theoretically) easy to obtain. This is both a legal and a technological angle, with the legal part being the question of who owns the land where the resource is found. I suspect it’s no accident that, of the nine countries Wikipedia lists as having major gold rushes in the 19th century, eight of them were areas colonized by Europeans, with Greece as the sole outlier. In places like Australia, Venezuela, and the United States, a frontier mentality prevailed which facilitated the idea that any random guy could move in and start panning for gold. Try the same trick in England of the same era, and the landowner will have words and possibly bullets for you — not to mention the unlikelihood of finding major gold deposits not already under exploitation.

At least, easily accessible ones. This is the technological side of the equation: if extracting the resource requires sophisticated training and/or expensive equipment, then that’s going to limit active parties to the well funded, well organized operations. These days a lot of our mineral extraction involves digging up ore, sometimes from deep underground, and subjecting it to complex chemical and physical processes. It’s a far cry from some guy with a pan on the bank of a stream believing he might strike it rich.

And finally, people have to hear about it. This seems like an easy requirement to meet, but again, notice that “gold rush” is a phrase we associate with the nineteenth century. There are a handful from earlier — all of them in the context of Spanish and Portuguese colonization of the Americas — but the mass communication of newspapers and especially the electric telegraph made it vastly easier to spread the news widely, creating a large pool of hopeful prospectors willing to pack up their lives and go in search of fortune.

(You might think, by the way, that the accessibility of the location might matter. One look at the Klondike Gold Rush, however, puts paid to that notion. People were willing to risk freezing off their body parts, dying of starvation, being eaten by bears, or falling off a mountain to get to where there was gold. It certainly does help if it’s easier to get to, especially if there are ships or trains, but it’s not a requirement.)

That mass media thing, of course, cuts both ways. Whoever first discovers the resource probably doesn’t want anybody to know about it! Marshall and Sutter at Sutter’s Mill in 1848 wanted to keep their gold to themselves. Alas, despite oaths of secrecy, the guy they sent to secure mineral rights for their land blabbed the tale repeatedly along the way and failed in his mission to boot. Sutter not only didn’t get to keep the gold to himself, but lost all his workers to prospecting, his crops and cattle to squatters, and his entire dream of a profitable agricultural rancho there.

Of course, not everybody who rushes to a source of gold, silver, diamonds, or any other valuable material makes their fortune. In fact, the vast majority of them don’t. Advantage goes to those who get there first, as they stake out and deplete the best claims — which of course contributes to the feverish sense of urgency, people making snap decisions rather than thinking it through. Between the cost of getting there, the cost of equipment (which may not be specialized but is still an expense for the kind of poor man hoping to strike it rich), and the cost of supporting yourself and any allies or employees in the wilderness, most people start out in the hole. In the California Gold Rush, it’s estimated that a few lucky souls truly acquired a fortune, about half made a modest profit, and the rest lost their shirts.

Which is why the actual smart move — albeit the much less glamorous one — is to be the guy selling picks and shovels. It was less than two months after the discovery at Sutter’s Mill that Samuel Brannan bought every piece of prospecting equipment he could find and opened a store in the then-tiny town of San Francisco, so he could sell those things to the people he knew would come — knew in part because he was also one of the first people to publicize the discovery! (The story goes that he couldn’t put it in his newspaper because all his staff had run off, so instead he walked through the streets with a vial of gold, shouting about it to everyone who could hear.) Selling pans at seventy-five times the price he paid for them, he made out like a bandit and became enormously wealthy.

Selling picks and shovels is also a lot safer. Any time riches or the dream of them are at stake, you’re going to get people fighting over them, and a gold rush is no different. Claim-jumping is the act of starting to work on a site someone else has claimed as their own — usually not while they’re conducting active operations, but if they haven’t gotten to it yet or have decided it’s not as promising as another location, neither of which mean they’re ready to let you have it instead. Even when people respect those boundaries, any dispute is liable to escalate to fighting . . . and, of course, any pre-existing tensions are likely to be exacerbated by the tense conditions. Black, Latino, and Chinese miners — along with smaller numbers from other marginalized groups — faced particularly intense threats and bloodshed; it’s no accident that they were less likely to reap a profit than their white counterparts. Meanwhile, Native Americans were massacred by miners who wanted them out of the way.

This kind of thing is also environmentally disastrous, because the men (and much smaller number of women) chasing a vision of gold don’t care very much about anything else. Deforestation, soil runoff, and active pollution from toxic chemicals wreak havoc on the land and anybody relying on it for their survival. In just a few short years, this can transform not only the immediate landscape of the claims but anything downstream of them, and not for the better.

And all of these things could happen in a speculative world! Any planetary colonization scenario is ripe for it, so long as interstellar travel is available to the masses. Even something non-mineral, like the hunting of fantastical beasts could potentially look like a gold rush, if someone finds a critical use for their horns or hides or other body parts. As long as it’s local to a certain area, valuable, relatively easy to get, and advertised widely, the fever will take hold, and people will come.