This is the point of any store of value, to impose a natural risk management simply due to inherent stable demand for the underlying asset. It need not be a capital asset at all, merely have economic value that is not known to disappear even in the worst situation. In principle, this could be true of any industrial commodity, but gold and precious metals are generally favored because of their demand and rarity in nature, which reduces the risk of devaluation associated with increased production and supply.Is a college degree a store of value? Is un-credentialed education a store of value? Does it depend on whether or not the skill or knowledge suite has economic value that is known not to disappear in even the worst situations? A store of value must hold value across multiple possible scenarios.
Economic value means the thing (tangible or intangible) has value as an item of trade; that it is a thing for which others are willing to give up something(s) of their own.
Precious metals are favored because of their demand and rarity in nature. This means that across multiple scenarios, demand is less susceptible than most things to economic fluctuations, and that it is not something which ample supply renders less precious, because there isn't ample supply.
Consider this in terms of tradeable skills, and we arrive at my own definition of a valuable, resilient trade or skill set: that there is consistently high demand for it, and that it involves high skill -- in other words: is rare.
The notion of the demand side of value is a bit more complex than John Robb gives credit to in his insistence on developing a virtualizable component to one's livelihood. It can either be (1) virtualizable as JR suggests, in that it is always in demand somewhere and you can supply it from anywhere, or (2) needed ubiquitously locally just about everywhere. As long as it is a skill that takes substantial time, effort, or natural ability to learn or master (thus rare), it will hold value in either demand environment.
On a related note: new thought on the Farmer vs. Hunter/Gatherer archetype. The Farmer stores his value in tangible things--land, crops, tools, community; the Hunter/Gatherer--also the Gambler--stores value in his wits. He hones his wits, and relies on luck and skill to win out. He takes bigger risks because things are less certain and he has less say over how things go. The Farmer has more "stores" to get through hard times, and more control over nature, and thus is more of an incrementalist. In times of greater uncertainty, even the Farmer types will flip to Gambler mentality...after all, if it's a mad scramble for survival, and a greater and greater proportion of people are likely to get screwed--or when the Farmer type loses his sense of control over his own destiny (due to endemic insecurity, financial meltdowns, excessive centralized bureaucracies moving people about willy-nilly, a faltering, uncertain economy, climate change, terrorism, whatever) than he'll throw caution to the wind and take bigger and bigger risks to try to be in the pool of the safe.