Using any medium of exchange other than agricultural/industrial commodities or labor barter is an abstraction of value. In that sense, silver, gold, platinum, palladium, uranium, et. al. (except mineral carbon which can be burned for fuel or heat), diamonds, rubies, emeralds; wampum, beads, shells, feathers, and lastly, Central Bank Notes from any issuing country distort the notion of value to the human being. Value would have originally been assigned on the basis of improving the conditions of life. Since that is no longer much of an issue except for the most disenfranchised in the world, commerce takes place with authorized media- before 1932, in european man's world: gold. Now it's slips of cloth- and plastic-paper...makes no difference really except that if there is collapse- the knee jerk reaction of europeans may be to place more value on chunks of metal...for a while...because without improvement in conditions...ultimately you can't eat metal...